U.S. patent application number 16/631443 was filed with the patent office on 2020-07-02 for semi-continuous filaments including a crystalline polyolefin and a hydrocarbon tackifier resin, and process for making same.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Saurabh Batra, Zackary J. Becker, Michael R. Berrigan, Eugene G. Joseph, Liyun Ren, Michael D. Romano, John D. Stelter, Sachin Talwar, Jacob J. Thelen.
Application Number | 20200208314 16/631443 |
Document ID | / |
Family ID | 65232443 |
Filed Date | 2020-07-02 |
![](/patent/app/20200208314/US20200208314A1-20200702-M00001.png)
United States Patent
Application |
20200208314 |
Kind Code |
A1 |
Joseph; Eugene G. ; et
al. |
July 2, 2020 |
SEMI-CONTINUOUS FILAMENTS INCLUDING A CRYSTALLINE POLYOLEFIN AND A
HYDROCARBON TACKIFIER RESIN, AND PROCESS FOR MAKING SAME
Abstract
Nonwoven webs including one or more semi-continuous filaments
made of a mixture including from about 50% w/w to about 99% w/w of
at least one crystalline polyolefin (co)polymer, and from about 1%
w/w to about 40% w/w of at least one hydrocarbon tackifier resin.
The at least one semi-continuous filament exhibits molecular
orientation, and at least one of the crystalline polyolefin
(co)polymer or the nonwoven web exhibits a Heat of Fusion measured
using Differential Scanning Calorimetry of greater than 50
Joules/g. A process for making the semi-continuous filaments and
nonwoven webs is also disclosed.
Inventors: |
Joseph; Eugene G.;
(Blacksburg, VA) ; Batra; Saurabh; (Minneapolis,
MN) ; Berrigan; Michael R.; (Oakdale, MN) ;
Stelter; John D.; (Osceola, WI) ; Thelen; Jacob
J.; (Minneapolis, MN) ; Becker; Zackary J.;
(St. Paul, MN) ; Ren; Liyun; (Woodbury, MN)
; Talwar; Sachin; (Woodbury, MN) ; Romano; Michael
D.; (Circle Pines, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
65232443 |
Appl. No.: |
16/631443 |
Filed: |
July 30, 2018 |
PCT Filed: |
July 30, 2018 |
PCT NO: |
PCT/IB2018/055686 |
371 Date: |
January 15, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62539242 |
Jul 31, 2017 |
|
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62700931 |
Jul 20, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D01D 5/088 20130101;
D04H 1/4291 20130101; D01F 1/10 20130101; D01F 6/04 20130101; D01D
5/0985 20130101 |
International
Class: |
D04H 1/4291 20060101
D04H001/4291; D01F 1/10 20060101 D01F001/10; D01F 6/04 20060101
D01F006/04; D01D 5/088 20060101 D01D005/088 |
Claims
1. A nonwoven web, comprising: at least one semi-continuous
filament comprising from about 50% w/w to about 99% w/w of at least
one crystalline polyolefin (co)polymer, and from about 1% w/w to
about 40% w/w of at least one hydrocarbon tackifier resin, wherein
the at least one semi-continuous (co)polymeric filament exhibits
molecular orientation, and further wherein the nonwoven web
exhibits a Heat of Fusion measured using Differential Scanning
Calorimetry of greater than 50 Joules/g.
2. The nonwoven web of claim 1, wherein the at least one
crystalline polyolefin (co)polymer is selected from the group
consisting of polyethylene, isotactic polypropylene, syndiotactic
polypropylene, isotactic polybutylene, syndiotactic polybutylene,
poly-4-methyl pentene, and mixtures thereof.
3. The nonwoven web of claim 2, wherein the at least one
crystalline polyolefin (co)polymer exhibits a Heat of Fusion
measured greater than 50 Joules/g.
4. The nonwoven web of claim 1, wherein the at least one
hydrocarbon tackifier resin is a saturated hydrocarbon.
5. The nonwoven web of claim 1, wherein the at least one
hydrocarbon tackifier resin is selected from the group consisting
of C.sub.5 piperylene derivatives, C.sub.9 resin oil derivatives,
and mixtures thereof.
6. The nonwoven web of claim 1, wherein the at least one
hydrocarbon tackifier resin makes up from 2% to 40% by weight of
the (co)polymeric filaments.
7. The nonwoven web of claim 6, wherein the at least one
hydrocarbon tackifier resin makes up from 5% to 30% by weight of
the (co)polymeric filaments.
8. The nonwoven web of claim 7, wherein the at least one
hydrocarbon tackifier resin makes up from 7% to 20% by weight of
the (co)polymeric filaments.
9. The nonwoven web of claim 1, wherein the at least one
(co)polymeric filament exhibits a mean Actual Filament Diameter of
less than 5 micrometers as determined using the Optical Microscopy
Test.
10. The nonwoven web of claim 1, wherein the at least one
(co)polymeric filament exhibits a mean Actual Filament Diameter of
from about 4 micrometers to about 10 micrometers, inclusive, as
determined using the Optical Microscopy Test.
11. The nonwoven web of claim 1, further comprising between 0 to
about 30% of at least one plasticizer.
12. The nonwoven web of claim 11, wherein the at least one
plasticizer is selected from the group consisting of oligomers of
C.sub.5 to C.sub.14 olefins, and mixtures thereof.
13. The nonwoven web of claim 1, wherein the nonwoven web exhibits
a Maximum Load in the Machine Direction of at least 40 Newtons as
measured using the Tensile Strength Test.
14. The nonwoven web of claim 1, wherein the nonwoven web exhibits
a Basis Weight of from 1 gsm to 400 gsm, inclusive, optionally
wherein the Basis Weight is from 1 gsm to 50 gsm.
15. The nonwoven web of claim 1, wherein the nonwoven web exhibits
a Stiffness of at least 800 mg as measured using the Stiffness
Test.
16. A process for making a nonwoven web, comprising: a) heating a
mixture of about 50% w/w to about 99% w/w of at least one
crystalline polyolefin (co)polymer, and from about 1% w/w to about
40% w/w of at least one hydrocarbon tackifier resin to at least a
Melting Temperature of the mixture to form a molten mixture; b)
extruding the molten mixture through at least one orifice to form
at least one semi-continuous filament; c) attenuating the at least
one semi-continuous filament to draw and molecularly orient the at
least one semi-continuous filament; and d) cooling the at least one
semi-continuous filament to a temperature below the Melting
Temperature of the molten mixture to form a nonwoven web, wherein
the at least one semi-continuous (co)polymeric filament exhibits
molecular orientation, and further wherein at least one of the
crystalline polyolefin (co)polymer or the nonwoven web exhibits a
Heat of Fusion measured using Differential Scanning Calorimetry of
greater than 50 Joules/g.
17. The process of claim 16, wherein extruding the mixture through
at least one orifice to form the at least one semi-continuous
filament is accomplished using a melt-spinning process.
18. The process of claim 16, further comprising at least one of
addition of a plurality of staple filaments to the at least one
semi-continuous filament, or addition of a plurality of
particulates to the at least one semi-continuous filament.
19. The process of claim 16, further comprising collecting the at
least one semi-continuous filament as the nonwoven web on a
collector.
20. The process of claim 19, further comprising processing the
collected nonwoven web using a process selected from the group
consisting of autogenous bonding, through-air bonding, electret
charging, calendering, embossing, needle-punching, needle tacking,
hydroentangling, or a combination thereof.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to semi-continuous filaments
including a crystalline polyolefin (co)polymer and a hydrocarbon
tackifier resin, and more particularly, to nonwoven webs including
such filaments, and methods for preparing such nonwoven webs.
BACKGROUND
[0002] Melt-spinning is a process for forming nonwoven webs of
thermoplastic (co)polymeric filaments. In a typical melt-spinning
process, one or more thermoplastic (co)polymer streams are extruded
through a die containing one or more orifices and attenuated form
micro-filaments, which are collected to form a melt-spun nonwoven
web.
[0003] Thermoplastic (co)polymers commonly used in forming
conventional melt-spun nonwoven webs include polyethylene (PE) and
polypropylene (PP). Melt-spun nonwoven webs are used in a variety
of applications, including acoustic and thermal insulation,
filtration media, surgical drapes, and wipes, among others.
SUMMARY
[0004] Briefly, in one aspect, the present disclosure describes a
nonwoven web including at least one semi-continuous filament
including from about 50% w/w to about 99% w/w of at least one
crystalline polyolefin (co)polymer, and from about 1% w/w to about
40% w/w of at least one hydrocarbon tackifier resin. The at least
one semi-continuous filament exhibits molecular orientation, and
the nonwoven web exhibits a Heat of Fusion measured using
Differential Scanning Calorimetry of greater than 50 Joules/g.
Preferably. the at least one semi-continuous filament comprises a
plurality of melt-spun filaments. Preferably, the at least one
semi-continuous filament is subjected to a filament bonding step
before, during, or after collection, thereby forming a spun-bond
web.
[0005] In some exemplary embodiments, the at least one crystalline
polyolefin (co)polymer is selected from polyethylene, isotactic
polypropylene, syndiotactic polypropylene, isotactic polybutylene,
syndiotactic polybutylene, poly-4-methyl pentene), and mixtures
thereof. In certain presently preferred embodiments, the at least
one crystalline polyolefin (co)polymer exhibits a Heat of Fusion
measured using Differential Scanning Calorimetry of greater than 50
Joules/g. In some such presently preferred embodiments, the at
least one crystalline polyolefin (co)polymer is selected to be
isotactic polypropylene, syndiotactic polypropylene, and mixtures
thereof.
[0006] In certain exemplary embodiments, the at least one
hydrocarbon tackifier resin is a saturated hydrocarbon. In certain
presently preferred exemplary embodiments, the at least one
hydrocarbon tackifier resin is selected from C.sub.5 piperylene
derivatives, C.sub.9 resin oil derivatives, and mixtures thereof.
In additional presently preferred exemplary embodiments, the at
least one hydrocarbon tackifier resin makes up from 2% to 40% by
weight of the (co)polymeric filaments, more preferably from 5% to
30% by weight of the (co)polymeric filaments, even more preferably
from 7% to 20% by weight of the (co)polymeric filaments.
[0007] In certain exemplary embodiments, the filaments further
include between about 0 to 30% w/w of at least one plasticizer. In
some such embodiments, the at least one plasticizer is selected
from oligomers of C.sub.5 to C.sub.14 olefins, and mixtures
thereof.
[0008] In further presently preferred exemplary embodiments, the
multiplicity of filaments exhibits a mean Actual Filament Diameter
of less than 5 micrometers as determined using the Optical
Microscopy Test as described herein. In other exemplary
embodiments, the multiplicity of melt-spun filaments exhibits a
mean Actual Filament Diameter of from about 1 micrometer to about
50 micrometers, inclusive; more preferably from 3 micrometers to 20
micrometers, inclusive; from 4 micrometers to 10 micrometers,
inclusive; as determined using the Optical Microscopy Test
described herein. 15.
[0009] In additional exemplary embodiments, the nonwoven web
exhibits a Stiffness of at least 800 mg as measured using the
Stiffness Test as described herein.
[0010] In another aspect, the present disclosure describes a
process for making a nonwoven web made up of at least one
semi-continuous filament, the process including heating a mixture
of about 50% w/w to about 99% w/w of at least one crystalline
polyolefin (co)polymer, and from about 1% w/w to about 40% w/w of
at least one hydrocarbon tackifier resin to at least a Melting
Temperature of the mixture to form a molten mixture, extruding the
molten mixture through at least one orifice to form at least one
semi-continuous filament, attenuating the at least one
semi-continuous filament to draw and molecularly orient the at
least one semi-continuous filament, and then cooling the at least
one semi-continuous filament to a temperature below the Melting
Temperature of the molten mixture to form a nonwoven web, The at
least one semi-continuous filament exhibits molecular orientation,
and at least one of the crystalline polyolefin (co)polymer or the
nonwoven web exhibits a Heat of Fusion measured using Differential
Scanning Calorimetry of greater than 50 Joules/g.
[0011] In further such exemplary embodiments, the at least one
semi-continuous filament comprises a plurality of semi-continuous
filaments, and the process further includes collecting the
plurality of semi-continuous filaments as the nonwoven web on a
collector. Preferably, the plurality of semi-continuous filaments
is comprised of melt-spun filaments. Preferably the melt-spun
filaments are subjected to a filament bonding step before, during,
or after collection, thereby producing a spun-bond nonwoven web. In
some such exemplary embodiments, the process further includes at
least one of addition of a plurality of staple filaments to the
plurality of semi-continuous filaments, or addition of a plurality
of particulates to the plurality of semi-continuous filaments.
[0012] In some exemplary embodiments, the process further includes
processing the collected nonwoven web using a process selected from
autogenous bonding, through-air bonding, electret charging,
embossing, needle-punching, needle tacking, hydroentangling, or a
combination thereof.
[0013] Exemplary embodiments according to the present disclosure
may have certain surprising and unexpected advantages over the art.
One such advantage of exemplary embodiments of the present
disclosure relates to increased tensile strength exhibited by the
webs, even when prepared at low Basis Weight (i.e., less than or
equal to 50 g/m.sup.2, "gsm"). Increased tensile strength for low
Basis Weight webs is important for many insulation applications,
for example, thermal or acoustic insulation, more particularly
acoustic or thermal insulation mats used in motor vehicles (e.g.,
aircraft, trains, automobiles, trucks, ships, and
submersibles).
[0014] Thus, exemplary nonwoven webs as described herein may
advantageously exhibit a Maximum Load in the Machine Direction
Maximum Tensile Load in the Machine Direction as measured with the
Tensile Strength Test as defined herein, of at least 40 Newtons
(N), at least 50 N, at least 75 N, at least 100 N, at least 125 N,
or even at least 150 N; and generally no greater than 1,000 N, 750
N, 500 N, or 250 N.
[0015] In other exemplary embodiments, the nonwoven webs as
described herein may advantageously exhibit improved Stiffness, as
evidenced by a Stiffness measured with the
[0016] Stiffness Test as defined herein, of at least 800 mg, 900
mg, 1,000 mg, 1500 mg, or even 2,000 mg; and generally no greater
than 5,000 mg, 4,000 mg, 3,000 mg, or 2,500 mg.
[0017] In certain exemplary embodiments, the nonwoven webs exhibit
a Basis Weight of from 1 g/m.sup.2 (gsm) to 400 gsm, more
preferably from 1 gsm to 200 gsm, even more preferably from 1 gsm
to 100 gsm, or even 1 gsm to about 50 gsm.
[0018] Another advantage of exemplary embodiments relates to an
increased ability to stretch the filaments by increasing the
attenuation pressure without filament breakage, thus leading to
higher filament spinning speeds and smaller diameter filaments. In
some such embodiments, this may also advantageously limit or
eliminate the possibility of newly formed filaments breaking and
forming filament fragments ((i.e., "fly") which can fall onto the
collected nonwoven web and degrade the appearance of the web where
they land.
[0019] An additional advantage of exemplary embodiments relates to
an ability to use a higher melt temperature for the melt-spun
process, which leads to a lower mean Actual Filament Diameter (AFD)
of about 5 micrometers or less, and may even permit the production
of sub-micrometer filaments (i.e., nanofilaments) having a mean
Actual Filament Diameter (AFD) of less than one micrometer. Such
nonwoven webs including sub-micrometer filaments achieve better
acoustic and/or thermal insulation performance at equal or lower
Basis Weight than comparable microfilament webs, thus leading to
improved insulation performance at a lower production cost.
Embodiments of the present disclosure may also exhibit higher
production rates due to the lower melt viscosities achieved during
melt-spinning of the filaments.
[0020] The following Listing of Exemplary Embodiments summarizes
the various exemplary illustrative embodiments of the present
disclosure.
Listing of Exemplary Embodiments
[0021] A. A nonwoven web, comprising:
[0022] at least one semi-continuous filament comprising from about
50% w/w to about 99% w/w of at least one crystalline polyolefin
(co)polymer, and
[0023] from about 1% w/w to about 40% w/w of at least one
hydrocarbon tackifier resin, wherein the at least one
semi-continuous filament exhibits molecular orientation, and
further wherein the melt-spun nonwoven web exhibits a Heat of
Fusion measured using Differential Scanning Calorimetry of greater
than 50 Joules/g.
B. The nonwoven web of Embodiment A or any following Embodiment,
wherein the at least one crystalline polyolefin (co)polymer is
selected from the group consisting of polyethylene, isotactic
polypropylene, syndiotactic polypropylene, isotactic polybutylene,
syndiotactic polybutylene, poly-4-methyl pentene, and mixtures
thereof. C. The nonwoven web Embodiment B, wherein the at least one
crystalline polyolefin (co)polymer exhibits a Heat of Fusion
measured using Differential Scanning Calorimetry of greater than 50
Joules/g, D. The nonwoven web of any preceding or following
Embodiment, wherein the at least one hydrocarbon tackifier resin is
a saturated hydrocarbon. E. The nonwoven web of any preceding or
following Embodiment, wherein the at least one hydrocarbon
tackifier resin is selected from the group consisting of C.sub.5
piperylene derivatives, C.sub.9 resin oil derivatives, and mixtures
thereof. F. The nonwoven web of any preceding or following
Embodiment, wherein the at least one hydrocarbon tackifier resin
makes up from 1% to 40% by weight of the (co)polymeric filaments.
G. The nonwoven web of claim Embodiment F, wherein the at least one
hydrocarbon tackifier resin makes up from 5% to 30% by weight of
the (co)polymeric filaments. H. The nonwoven web of Embodiment G,
wherein the at least one hydrocarbon tackifier resin makes up from
7% to 20% by weight of the (co)polymeric filaments. I. The nonwoven
web of any preceding or following Embodiment, further comprising
between about 0 to 30% of at least one plasticizer. J. The nonwoven
web of Embodiment H, wherein the at least one plasticizer is
selected from the group consisting of oligomers of C.sub.5 to
C.sub.14 olefins, and mixtures thereof. K. The nonwoven web of any
preceding or following Embodiment, wherein the nonwoven web
exhibits a Maximum Load in the Machine Direction of at least 40
Newtons as measured using the Tensile Strength Test described
herein. L. The nonwoven web of any preceding or following
Embodiment, wherein the nonwoven web exhibits a Stiffness of at
least 800 mg as measured using the Stiffness Test described herein.
M. The melt-spun nonwoven web of any preceding or following
Embodiment, wherein the nonwoven web exhibits a Basis Weight of 1
gsm to 400 gsm, preferably wherein the nonwoven web exhibits a
Basis Weight of 1 gsm to 50 gsm. N. The melt-spun nonwoven web of
any preceding Embodiment, wherein the plurality of (co)polymeric
filaments exhibits a mean Actual Filament Diameter of less than
five micrometers as determined using the Optical Microscopy Test
described herein. O. The melt-spun nonwoven web of any one of
Embodiments A-M, wherein the at least one (co)polymeric filament
exhibits a mean Actual Filament Diameter of from about 4
micrometers to about 10 micrometers, inclusive, as determined using
the Optical Microscopy Test described herein. P. A process for
making a melt-spun nonwoven web, comprising:
[0024] a) heating a mixture of about 50% w/w to about 99% w/w of at
least one crystalline polyolefin (co)polymer, and from about 1% w/w
to about 40% w/w of at least one hydrocarbon tackifier resin to at
least a Melting Temperature of the mixture to form a molten
mixture;
[0025] b) extruding the molten mixture through at least one orifice
to form at least one semi-continuous filament;
[0026] c) attenuating the at least one semi-continuous filament to
draw and molecularly orient the at least one semi-continuous
filament; and
[0027] d) cooling the at least one semi-continuous filament to a
temperature below the Melting Temperature of the molten mixture to
form a nonwoven web, wherein the at least one semi-continuous
filament exhibits molecular orientation, and further wherein at
least one of the crystalline polyolefin (co)polymer or the nonwoven
web exhibits a Heat of Fusion measured using Differential Scanning
Calorimetry of greater than 50 Joules/g.
Q. The process of Embodiment P, wherein extruding the mixture
through at least one orifice to form the at least one
semi-continuous filament is accomplished using a melt-spinning
process. R. The process of Embodiment P or Q, further comprising at
least one of addition of a plurality of staple filaments to the at
least one semi-continuous filament, or addition of a plurality of
particulates to the at least one semi-continuous filament. S. The
process of any one of embodiments P, Q, or R, further comprising
collecting the at least one semi-continuous filament as the
melt-spun nonwoven web on a collector. T. The process of Embodiment
S, further comprising processing the collected nonwoven web using a
process selected from the group consisting of autogenous bonding,
through-air bonding, electret charging, calendering, embossing,
needle-punching, needle tacking, hydroentangling, or a combination
thereof.
[0028] Various aspects and advantages of exemplary embodiments of
the disclosure have been summarized. The above Summary is not
intended to describe each illustrated embodiment or every
implementation of the present certain exemplary embodiments of the
present disclosure. The Detailed Description and Examples that
follow more particularly exemplify certain presently preferred
embodiments using the principles disclosed herein.
DETAILED DESCRIPTION
[0029] For the following Glossary of defined terms, these
definitions shall be applied for the entire application, unless a
different definition is provided in the claims or elsewhere in the
specification.
Glossary
[0030] Certain terms are used throughout the description and the
claims that, while for the most part are well known, may require
some explanation. It should be understood that:
[0031] The terms "(co)polymer" or "(co)polymers" includes
homopolymers and copolymers, as well as homopolymers or copolymers
that may be formed in a miscible blend, e.g., by coextrusion or by
reaction, including, e.g., transesterification. The term
"copolymer" includes random, block and star (e.g. dendritic)
copolymers.
[0032] The term "molecularly same (co)polymer" means one or more
(co)polymers that have essentially the same repeating molecular
unit, but which may differ in molecular weight, method of
manufacture, commercial form, and the like.
[0033] The term "homogeneous" means exhibiting only a single phase
of matter when observed at a macroscopic scale.
[0034] The term "Actual Filament Diameter" or "AFD" means the mean
number diameter determined by measuring 20 individual filaments
using the Optical Microscopy Test described herein.
[0035] The term "Effective Filament Diameter" or "EFD" means the
apparent diameter of the filaments in a nonwoven web based on an
air permeation test in which air at 1 atmosphere and room
temperature is passed at a face velocity of 5.3 cm/sec through a
web sample of known thickness, and the corresponding pressure drop
is measured. Based on the measured pressure drop, the Effective
Filament Diameter is calculated as set forth in Davies, C. N., The
Separation of Airborne Dust and Particles, Institution of
Mechanical Engineers, London Proceedings, 1B (1952).
[0036] The term "microfilaments" means a population of filaments
having a mean AFD of at least one micrometer (.mu.m) and preferably
less than 1,000 .mu.m.
[0037] The term "coarse microfilaments" means a population of
microfilaments having a mean AFD of at least 10 .mu.m and
preferably less than or equal to 100 .mu.m.
[0038] The term "fine microfilaments" means a population of
microfilaments having a mean AFD of from one .mu.m to 20 .mu.m,
inclusive.
[0039] The term "ultrafine microfilaments" means a population of
microfilaments having a mean AFD of from one .mu.m to 10 .mu.m,
inclusive.
[0040] The term "sub-micrometer filaments" means a population of
filaments having a mean AFD of less than 1 .mu.m.
[0041] The term "nanofilaments" means a population of filaments
having a mean AFD of less than 1 .mu.m.
[0042] The term "semi-continuous" with reference to a filament
means that the filament is of finite but indeterminate length, the
length of the filament being on the order of at least a factor of
1,000; 5,000; 10,000; 50,000; 100,000; or more times the Actual
Fiber Diameter.
[0043] The terms "molecularly orient" and "molecular orientation"
with reference to a single filament means that at least a
substantial portion of the (co)polymer molecules making up the
filament are aligned along the longitudinal axis of the
filament.
[0044] The terms "particle" and "particulate" are used
substantially interchangeably. Generally, a particle or particulate
means a small distinct piece or individual part of a material in
finely divided form. However, a particulate may also include a
collection of individual particles associated or clustered together
in finely divided form. Thus, individual particles used in certain
exemplary embodiments of the present disclosure may clump,
physically intermesh, electro-statically associate, or otherwise
associate to form particulates. In certain instances, particulates
in the form of agglomerates of individual particles may be
intentionally formed such as those described in U.S. Pat. No.
5,332,426 (Tang et al.).
[0045] The term "nonwoven web" means a web characterized by
entanglement or point bonding of at least one semi-continuous
filament and preferably a plurality of semi-continuous
filaments.
[0046] The term "composite nonwoven web" means a nonwoven web
including at least one of a plurality of filaments and a plurality
of particulates.
[0047] The term "particle-loaded nonwoven web" means a composite
nonwoven web containing particles bonded to the filaments or
enmeshed among the filaments, the particles optionally being
absorbent and/or adsorbent.
[0048] The term "enmeshed" means that particles are distributed and
physically held in the filaments of the web. Generally, there is
point and line contact along the filaments and the particles so
that nearly the full surface area of the particles is available for
interaction with a fluid.
[0049] The term "self-supporting" with reference to a nonwoven web
means a nonwoven web having sufficient coherency and strength so as
to be drape-able and handle-able without substantial tearing or
rupture.
[0050] The terms "melt-spinning" and "spun-bonding" mean processes
for forming a nonwoven web by extruding a filament-forming material
through one or more orifices to form at least one semi-continuous
filament, attenuating the at least one semi-continuous filament by
drawing the filament, and thereafter collecting a layer of the
attenuated at least one semi-continuous filament, and, for
spun-bonding, bonding the attenuated at least one semi-continuous
filament before, during and/or after collection on a collector.
[0051] The term "die" means a processing assembly including one or
more orifices for use in a process for extruding a molten
(co)polymer mixture to form one or more semi-continuous
filament(s), such process including but not limited to
melt-spinning and/or spun-bonding processes.
[0052] The term "melt-spun filament(s)" means one or more
semi-continuous filament(s) prepared using a melt-spinning
process.
[0053] The term "spun-bond filaments(s)" means one or more
semi-continuous filament(s) prepared using a melt-spinning process,
wherein the one or more semi-continuous filament(s) are bonded
together at one or more contact points along the surface(s) of the
filament(s).
[0054] The term "calendering" means a process of passing a nonwoven
web through rollers to obtain a compressed material. The rollers
may optionally be heated, in which case bonding together of the
components of the nonwoven web may be achieved.
[0055] The term "autogenous bonding" means bonding between
filaments at an elevated temperature as obtained in an oven or with
a through-air bonder without application of solid contact pressure
such as in point-bonding or calendering.
[0056] The term "densification" means a process whereby filaments
which have been deposited either directly or indirectly onto a
filter winding arbor or mandrel are compressed, either before or
after the deposition, and made to form an area, generally or
locally, of lower porosity, whether by design or as an artifact of
some process of handling the forming or formed filter.
Densification also includes the process of calendering webs.
[0057] The term "machine direction" means the longitudinal
direction in which a nonwoven web of indeterminate length is moved
or wound onto a collector, and is distinguished from the
"cross-web" direction, which is the lateral direction extending
between the two lateral edges of the nonwoven web. Generally, the
cross-web direction is orthogonal to the machine direction for a
rectangular nonwoven web.
[0058] The term "Web Basis Weight" is calculated from the weight of
a 10 cm.times.10 cm web sample.
[0059] The term "Web Thickness" is measured on a 10 cm.times.10 cm
web sample using a thickness testing gauge having a tester foot
with dimensions of 5 cm.times.12.5 cm at an applied pressure of 150
Pa.
[0060] The term "Polymer Density" is the mass per unit volume of
the (co)polymer or (co)polymer blend that is used to form the
nonwoven filaments of a nonwoven web. The Polymer Density for a
(co)polymer may generally be found in the literature, and the
Polymer Density of a (co)polymer blend may be calculated from the
weighted average of the component (co)polymer Polymer Densities,
based upon the weight percentages of the individual (co)polymers
used to make up the (co)polymer blend. The Polymer Density of
polypropylene resin is 0.91 g/cm.sup.3 and the Polymer Density of
the hydrocarbon tackifier resins used herein is about 1.00
g/cm.sup.3. For the calculations of Solidity provided herein using
the following formula, a Polymer Density of 0.91 g/cm.sup.3 was
used.
[0061] The term "Solidity" is defined by the equation:
Solidity (%) = [ 3.937 * Web Basis Weight ( g / m 2 ) ] [ Web
Thickness ( mils ) * Polymer Density ( g / cm 3 ) ]
##EQU00001##
wherein one mil is equivalent to 25 micrometers.
[0062] The term "Melting Temperature" as used herein, is the
highest magnitude peak among principal and any secondary
endothermic melting peaks in a cooling after first heating heat
flow curve plotted as a function of temperature, as obtained using
Differential Scanning Calorimetry (DSC).
[0063] The term "adjoining" with reference to a particular layer in
a multi-layer nonwoven web means joined with or attached to another
layer, in a position wherein the two layers are either next to
(i.e., adjacent to) and directly contacting each other, or
contiguous with each other but not in direct contact (i.e., there
are one or more additional layers intervening between the
layers).
[0064] The terms "about" or "approximately" with reference to a
numerical value or a shape means +/- five percent of the numerical
value or property or characteristic, but expressly includes the
exact numerical value. For example, a viscosity of "about" 1 Pa-sec
refers to a viscosity from 0.95 to 1.05 Pa-sec, but also expressly
includes a viscosity of exactly 1 Pa-sec. Similarly, a perimeter
that is "substantially square" is intended to describe a geometric
shape having four lateral edges in which each lateral edge has a
length which is from 95% to 105% of the length of any other lateral
edge, but which also includes a geometric shape in which each
lateral edge has exactly the same length.
[0065] The term "substantially" used with reference to a property
or characteristic means that the property or characteristic is
exhibited to a greater extent than the opposite of that property or
characteristic is exhibited. For example, a substrate that is
"substantially" transparent refers to a substrate that transmits
more radiation (e.g. visible light) than it fails to transmit (e.g.
absorbs and reflects). Thus, a substrate that transmits more than
50% of the visible light incident upon its surface is substantially
transparent, but a substrate that transmits 50% or less of the
visible light incident upon its surface is not substantially
transparent.
[0066] By using terms of orientation such as "atop", "on", "over,"
"covering", "uppermost", "underlying" and the like for the location
of various elements in the disclosed coated articles, we refer to
the relative position of an element with respect to a
horizontally-disposed, upwardly-facing substrate. However, unless
otherwise indicated, it is not intended that the substrate or
articles should have any particular orientation in space during or
after manufacture.
[0067] By using the term "overcoated" to describe the position of a
layer with respect to a substrate or other element of an article of
the present disclosure, we refer to the layer as being atop the
substrate or other element, but not necessarily contiguous to
either the substrate or the other element.
[0068] By using the term "separated by" to describe the position of
a layer with respect to other layers, we refer to the layer as
being positioned between two other layers but not necessarily
contiguous to or adjacent to either layer.
[0069] As used in this specification and the appended embodiments,
the singular forms "a", "an", and "the" include plural referents
unless the content clearly dictates otherwise. Thus, for example,
reference to fine filaments containing "a compound" includes a
mixture of two or more compounds. As used in this specification and
the appended embodiments, the term "or" is generally employed in
its sense including "and/or" unless the content clearly dictates
otherwise.
[0070] As used in this specification, the recitation of numerical
ranges by endpoints includes all numbers subsumed within that range
(e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).
[0071] Unless otherwise indicated, all numbers expressing
quantities or ingredients, measurement of properties and so forth
used in the specification and embodiments are to be understood as
being modified in all instances by the term "about." Accordingly,
unless indicated to the contrary, the numerical parameters set
forth in the foregoing specification and attached listing of
embodiments can vary depending upon the desired properties sought
to be obtained by those skilled in the art utilizing the teachings
of the present disclosure. At the very least, and not as an attempt
to limit the application of the doctrine of equivalents to the
scope of the claimed embodiments, each numerical parameter should
at least be construed in light of the number of reported
significant digits and by applying ordinary rounding
techniques.
[0072] Various exemplary embodiments of the disclosure will now be
described. Exemplary embodiments of the present disclosure may take
on various modifications and alterations without departing from the
spirit and scope of the disclosure. Accordingly, it is to be
understood that the embodiments of the present disclosure are not
to be limited to the following described exemplary embodiments, but
are to be controlled by the limitations set forth in the claims and
any equivalents thereof.
Nonwoven Melt-Spun (Spun-Bond) Fibrous Webs
[0073] In one exemplary embodiment, the disclosure describes a
nonwoven web comprising at least one semi-continuous filament
including from about 50% w/w to about 99% w/w of at least one
crystalline polyolefin (co)polymer, and from about 1% w/w to about
40% w/w of at least one hydrocarbon tackifier resin, wherein the at
least one semi-continuous filament exhibits molecular orientation,
and further wherein the nonwoven web exhibits a Heat of Fusion
measured using Differential Scanning Calorimetry of greater than 50
Joules/g.
[0074] In some exemplary embodiments, the nonwoven webs as
described herein may advantageously exhibit improved tensile
strength, as evidenced by a Maximum Tensile Load in the Machine
Direction as measured with the Tensile Strength Test as defined
herein, of at least 40 Newtons (N), at least 50 N, at least 75 N,
at least 100 N, at least 125 N, or even at least 150 N; and
generally no greater than 1,000 N, 750 N, 500 N, or 250 N.
[0075] In other exemplary embodiments, the nonwoven webs as
described herein may advantageously exhibit improved Stiffness, as
evidenced by a Stiffness measured with the Stiffness Test as
defined herein, of at least 800 mg, 900 mg, 1,000 mg, 1500 mg, or
even 2,000 mg; and generally no greater than 5,000 mg, 4,000 mg,
3,000 mg, or 2,500 mg.
Nonwoven Webs Including Semi-Continuous Filaments
[0076] Nonwoven webs of the present disclosure generally include
one or more filaments that may be regarded as semi-continuous
filaments. In some exemplary embodiments, the one or more
semi-continuous filaments in the non-woven fibrous webs or
composite webs comprise one or more microfilaments and may
advantageously exhibit a mean Effective Filament Diameter
(determined using the test method described below) of from about 5
micrometers to about 20 micrometers, inclusive; more preferably
from about 7 micrometers to about 15 micrometers, inclusive, even
more preferably from about 8 micrometers to about 10 micrometers,
inclusive. In other exemplary embodiments, the semi-continuous
filaments in the non-woven fibrous webs or composite webs may
advantageously exhibit a mean Actual Filament Diameter (determined
using the test method described below) of from about 1 micrometer
to about 50 micrometers (.mu.m), inclusive; more preferably from 3
.mu.m to 20 .mu.m, inclusive; even more preferably from about 4
.mu.m to about 10 .mu.m or even to about 9 .mu.m, 8 .mu.m, 7 .mu.m,
6 .mu.m, or even 5 .mu.m, inclusive.
[0077] The nonwoven web may take a variety of forms, including
mats, webs, sheets, scrims, fabrics, and a combination thereof.
Semi-Continuous Filament Components
[0078] Nonwoven webs of the present disclosure comprise
semi-continuous filaments comprising from about 50% w/w to about
99% w/w of at least one crystalline polyolefin (co)polymer, and
from about 1% w/w to about 40% w/w at least one hydrocarbon
tackifier resin. In some embodiments, a single crystalline
polyolefin (co)polymer) may be mixed with a single hydrocarbon
tackifier resin. In other exemplary embodiments, a single
crystalline polyolefin (co)polymer may be advantageously mixed with
two or more hydrocarbon tackifier resins. In further exemplary
embodiments, two or more crystalline polyolefin (co)polymers may be
mixed with a single hydrocarbon tackifier resin. In other exemplary
embodiments, two or more crystalline polyolefin (co)polymers may be
advantageously mixed with two or more hydrocarbon tackifier
resins.
Crystalline Polyolefin (Co)Polymer
[0079] The crystalline polyolefin (co)polymers useful in practicing
embodiments of the present disclosure are generally crystalline
polyolefin (co)polymers with a moderate level of crystallinity.
Generally (co)polymer crystallinity arises from stereoregular
sequences in the (co)polymer, for example stereoregular ethylene,
propylene, or butylene sequences. For example, the (co)polymer can
be: (A) a propylene homopolymer in which the stereoregularity is
disrupted in some manner such as by regio-inversions; (B) a random
propylene copolymer in which the propylene stereoregularity is
disrupted at least in part by co-monomers; or (C) a combination of
(A) and (B).
[0080] In some exemplary embodiments, the at least one crystalline
polyolefin (co)polymer is selected from polyethylene, isotactic
polypropylene, syndiotactic polypropylene, isotactic polybutylene,
syndiotactic polybutylene, poly-4-methyl pentene, and mixtures
thereof. The at least one crystalline polyolefin (co)polymer
preferably exhibits a Heat of Fusion measured using Differential
Scanning Calorimetry of greater than 50 Joules/g. In certain
presently preferred exemplary embodiments, the at least one
crystalline polyolefin (co)polymer is selected to be isotactic
polypropylene, syndiotactic polypropylene, and mixtures
thereof.
[0081] In some exemplary embodiments, the crystalline polyolefin
(co)polymer is a (co)polymer that includes a non-conjugated diene
monomer to aid in vulcanization and other chemical modification of
the blend composition. The amount of diene present in the
(co)polymer is preferably less than 10% by weight, and more
preferably less than 5% by weight. The diene may be any
non-conjugated diene which is commonly used for the vulcanization
of ethylene propylene rubbers including, but not limited to,
ethylidene norbornene, vinyl norbornene, and dicyclopentadiene.
[0082] In one exemplary embodiment, the crystalline polyolefin
(co)polymer is a random copolymer of propylene and at least one
co-monomer selected from ethylene, C.sub.4-C.sub.12 alpha-olefins,
and combinations thereof. In one particular embodiment, the
copolymer includes ethylene-derived units in an amount ranging from
a lower limit of 2%, 5%, 6%, 8%, or 10% by weight to an upper limit
of 20%, 25%, or 28% by weight. This embodiment also includes
propylene-derived units present in the copolymer in an amount
ranging from a lower limit of 72%, 75%, or 80% by weight to an
upper limit of 98%, 95%, 94%, 92%, or 90% by weight. These
percentages by weight are based on the total weight of the
propylene and ethylene-derived units; i.e., based on the sum of
weight percent propylene-derived units and weight percent
ethylene-derived units being 100%.
[0083] In other exemplary embodiments, the crystalline polyolefin
(co)polymer is a random propylene copolymer having a narrow
compositional distribution. In certain presently preferred
embodiments, the crystalline polyolefin (co)polymer is a random
propylene copolymer exhibiting a Heat of Fusion determined using
DSC of greater than 50 J/g.
[0084] The copolymer is described as random because for a copolymer
comprising propylene, co-monomer, and optionally diene, the number
and distribution of co-monomer residues is consistent with the
random statistical polymerization of the monomers. In stereoblock
structures, the number of block monomer residues of any one kind
adjacent to one another is greater than predicted from a
statistical distribution in random copolymers with a similar
composition. Historical ethylene-propylene copolymers with
stereoblock structure have a distribution of ethylene residues
consistent with these blocky structures rather than a random
statistical distribution of the monomer residues in the
(co)polymer. The intramolecular composition distribution (i.e.,
randomness) of the copolymer may be determined by .sup.13C NMR,
which locates the co-monomer residues in relation to the
neighboring propylene residues.
[0085] The crystallinity of the crystalline polyolefin (co)polymers
may be expressed in terms of heat of fusion. Embodiments of the
present disclosure include crystalline polyolefin (co)polymers
exhibiting a heat of fusion as determined using differential
scanning Calorimetry (DSC) greater than 50 J/g, greater than 51
J/g, greater than 55 J/g, greater than 60 J/g, greater than 70 J/g,
greater than 80 J/g, greater than 90 J/g, greater than 100 J/g, or
even about 110 J/g. Generally, the crystalline polyolefin
(co)polymers exhibit a heat of fusion as determined using DSC less
than 210 J/g, less than 200 J/g, less than 190 J/g, less than 180
J/g. less than 170 J/g. less than 160 J/g, less than 150 J/g, less
than 140 J/g, less than 130 J/g, less than 120 J/g, less than 110
J/g, or even less than 100 J/g.
[0086] The level of crystallinity is also reflected in the Melting
Point. In one embodiment of the present disclosure, the (co)polymer
has a single Melting Point. Typically, a sample of propylene
(co)polymer will show secondary melting peaks adjacent to the
principal peak, which are considered together as a single Melting
Point. The highest of these peaks is considered to be the Melting
Point.
[0087] The crystalline polyolefin (co)polymer preferably has a
melting point determined using DSC ranging from an upper limit of
300.degree. C., 275.degree. C., 250.degree. C., 200.degree. C.,
175.degree. C., 150.degree. C., 125.degree. C., 110.degree. C., or
even about 105.degree. C., to a lower limit of about 105.degree.
C., 110.degree. C., 120.degree. C., 125.degree. C., 130.degree. C.,
140.degree. C., 150.degree. C., 160.degree. C., 175, 180.degree.
C., 190.degree. C., 200.degree. C., 225.degree. C., or even about
250.degree. C.
[0088] The crystalline polyolefin (co)polymers used in the
disclosure generally have a weight average molecular weight (Mw)
within the range having an upper limit of 5,000,000 Daltons (Da or
g/mol), 1,000,000 Da, or 500,000 Da, and a lower limit of 10,000
Da, 20,000 Da, or 80,000 Da, and a molecular weight distribution
W.sub.w/W.sub.n (MWD), sometimes referred to as a "polydispersity
index" (PDI), ranging from a lower limit of 1.5, 1.8, or 2.0 to an
upper limit of 40, 20, 10, 5, or 4.5. The M.sub.w and MWD, as used
herein, can be determined by a variety of methods, including those
in U.S. Pat. No. 4,540,753 to Cozewith, et al., and references
cited therein, such as those methods found in Verstrate et al.,
Macromolecules, v. 21, p. 3360 (1988), the descriptions of which
are incorporated by reference herein for purposes of U.S.
practices.
[0089] At least one crystalline polyolefin (co)polymer is generally
present in an amount from about 50% w/w (50.0% w/w, 55% w/w, 60%
w/w, 65% w/w, 70% w/w, 75% w/w, 80% w/w, 85% w/w, or even about 90%
w/w) to about 99% w/w (99.0% w/w, 98% w/w 97% w/w, 96% w/w, 95%
w/w, 90% w/w, 85% w/w, 80% w/w, 75% w/w, 70% w/w, 65% w/w, or even
about 60% w/w) based on the total weight of the composition.
Hydrocarbon Tackifier Resins
[0090] Various types of natural and synthetic hydrocarbon tackifier
resins, alone or in admixture with each other, can be used in
preparing the filament compositions described herein, provided they
meet the miscibility criteria described herein. Preferably, the
hydrocarbon tackifier resin is selected to be miscible (i.e., forms
a homogenous melt) with the crystalline polyolefin (co)polymer(s)
when the mixture is in a molten state, that is, when the mixture of
the at least one crystalline polyolefin (co)polymer and the at
least one hydrocarbon tackifier resin is heated to a temperature at
or above the Melting Temperature (as determined using DSC) of the
mixture.
[0091] Suitable resins include, but are not limited to, natural
rosins and rosin esters, hydrogenated rosins and hydrogenated rosin
esters, coumarone-indene resins, petroleum resins, polyterpene
resins, and terpene-phenolic resins. Specific examples of suitable
petroleum resins include, but are not limited to aliphatic
hydrocarbon tackifier resins, hydrogenated aliphatic hydrocarbon
tackifier resins, mixed aliphatic and aromatic hydrocarbon
tackifier resins, hydrogenated mixed aliphatic and aromatic
hydrocarbon tackifier resins, cycloaliphatic hydrocarbon tackifier
resins, hydrogenated cycloaliphatic resins, mixed cycloaliphatic
and aromatic hydrocarbon tackifier resins, hydrogenated mixed
cycloaliphatic and aromatic hydrocarbon tackifier resins, aromatic
hydrocarbon tackifier resins, substituted aromatic hydrocarbons,
and hydrogenated aromatic hydrocarbon tackifier resins.
[0092] As used herein, "hydrogenated" includes fully, substantially
and at least partially hydrogenated resins. Suitable aromatic
resins include aromatic modified aliphatic resins, aromatic
modified cycloaliphatic resin, and hydrogenated aromatic
hydrocarbon tackifier resins. Any of the above resins may be
grafted with an unsaturated ester or anhydride to provide enhanced
properties to the resin. Examples of grafted resins and their
manufacture are described in the chapter titled Hydrocarbon Resins,
Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed. v. 13,
pp. 717-743 (J. Wiley & Sons, 1995).
[0093] Hydrocarbon tackifier resins suitable for use as described
herein include EMPR 100, 101, 102, 103, 104, 105, 106, 107, 108,
109, 110, 116, 117, and 118 resins, OPPERA.TM. resins, and EMFR
resins available from Exxon-Mobil Chemical Company (Spring, Tex.);
ARKON.TM. P140, P125, P115, M115, and M135 and SUPER ESTER.TM.
rosin esters available from Arakawa Chemical Company (Osaka,
Japan); SYLVARES.TM. polyterpene resins, styrenated terpene resins
and terpene phenolic resins, SYLVATAC.TM. and SYLVALITE.TM. rosin
esters available from Arizona Chemical Company LLC (Jacksonville,
Fla.); NORSOLENE.TM. aliphatic aromatic resins and WINGTACK.TM.
C.sub.5 resins available from TOTAL Cray Valley (Paris, France);
DERTOPHENE.TM. terpene phenolic resins and DERCOLYTE.TM.
polyterpene resins available from DRT Chemical Company (Dax Cedex,
France); EASTOTAC.TM. resins, PICCOTAC.TM. resins, REGALITE.TM. and
REGALREZ.TM. hydrogenated cycloaliphatic/aromatic resins available
from Eastman Chemical Company (Kingsport, Tenn.); PICCOLYTE.TM. and
PERMALYN.TM. polyterpene resins, rosins and rosin esters available
from Pinova, Inc. (Brunswick, Ga.); coumerone/indene resins
available from Neville Chemical Company (Pittsburg, Pa.);
QUINTONE.TM. acid modified C.sub.5 resins, C.sub.5-C.sub.9 resins,
and acid modified C.sub.5-C.sub.9 resins available from Nippon Zeon
(Tokyo, Japan); and CLEARON.TM. hydrogenated terpene resins
available from Yasuhara Chemical Company, Ltd. (Tokyo, Japan). The
preceding examples are illustrative only and by no means
limiting.
[0094] In some exemplary embodiments, the hydrocarbon tackifier
resin has a number average molecular weight (M.sub.n) within the
range having an upper limit of 5,000 Da, or 2,000 Da, or 1,000 Da,
and a lower limit of 200 Da, or 400 Da, or 500 Da; a weight average
molecular weight (M.sub.w) ranging from 500 Da to 10,000 Da or 600
to 5,000 Da or 700 to 4,000 Da; a Z average molecular weight
(M.sub.z) ranging from 500 Da to 10,000 Da, and a polydispersity
index (PDI) as measured by M.sub.w/M.sub.n, of from 1.5 to 3.5,
where M.sub.n, M.sub.w, and M.sub.z are determined using size
exclusion chromatography (SEC), or as provided by the supplier.
[0095] In other exemplary embodiments, the hydrocarbon tackifier
resin has a lower molecular weight than the crystalline polyolefin
(co)polymer.
[0096] The hydrocarbon tackifier resins of the present disclosure
are generally selected to be miscible with the crystalline
polyolefin (co)polymer in a molten state.
[0097] Hydrocarbon tackifier resins useful in embodiments of the
present disclosure may have a softening point within the range
having an upper limit of 180.degree. C., 150.degree. C., or
140.degree. C., and a lower limit of 80.degree. C., 120.degree. C.,
or 125.degree. C. Softening point (.degree. C.) is measured using a
ring and ball softening point device according to AS198 E-28
(Revision 1996).
[0098] Preferably, the hydrocarbon tackifier resin is a saturated
hydrocarbon. In certain presently preferred exemplary embodiments,
the hydrocarbon tackifier resin is selected from C.sub.5 piperylene
derivatives, C.sub.9 resin oil derivatives, and mixtures
thereof.
[0099] The hydrocarbon tackifier resin makes up from about 2% w/w
(2.0% w/w, 3% w/w, 4% w/w, 5% w/w, 10% w/w, 15% w/w, 20% w/w) to
about 40% (40.0% w/w, 35% w/w, 30% w/w, or even 25% w/w) based on
the weight of the (co)polymeric filaments in the nonwoven web, more
preferably from 5% to 30% by weight of the (co)polymeric filaments,
even more preferably from 7% to 20% by weight of the (co)polymeric
filaments.
Optional Nonwoven Web Components
[0100] In further exemplary embodiments, the nonwoven webs of the
present disclosure may further comprise one or more optional
components. The optional components may be used alone or in any
combination suitable for the end-use application of the nonwoven
webs. Three non-limiting, currently preferred optional components
include optional electret filament components, optional
non-melt-spun filament components, and optional particulate
components as described further below.
Optional Plasticizer
[0101] In certain exemplary embodiments, the (co)polymeric
filaments further include a plasticizer in an amount between about
0% to about 30% w/w of the filament composition, more preferably
from 1% to 20% w/w, 1% to 10% w/w, 1% to 5%, or even 1% to 2.5%. In
some such embodiments, the plasticizer is selected from oligomers
of C.sub.5 to C.sub.14 olefins, and mixtures thereof. A
non-limiting list of suitable commercially available plasticizers
includes SHF and SUPEERSYN.TM. available from Exxon-Mobil Chemical
Company (Houston, Tex.); STNFLUID.TM. available from
Chevron-Phillips Chemical Co. (Pasadena, Tex.); DURASYN.TM.
available from BP-Amoco Chemicals (London, England); NEXBASE.TM.
available from Fortum Oil and Gas Co. (Espoo, Finland); SYNTON.TM.
available from Crompton Corporation (Middlebury, Conn.); EMERY.TM.
available from BASF GmbH (Ludwigshafen, Germany), formerly Cognis
Corporation (Dayton, Ohio).
Optional Electret Fiber Component
[0102] The nonwoven webs of the present disclosure may optionally
comprise electret filaments. Suitable electret filaments are
described in U.S. Pat. Nos. 4,215,682; 5,641,555; 5,643,507;
5,658,640; 5,658,641; 6,420,024; 6,645,618, 6,849,329; and
7,691,168, the entire disclosures of which are incorporated herein
by reference.
[0103] Suitable electret filaments may be produced by meltblowing
filaments in an electric field, e.g. by melting a suitable
dielectric material such as a (co)polymer or wax that contains
polar molecules, passing the molten material through a
melt-spinning die to form discrete filaments, and then allowing the
molten (co)polymer to re-solidify while the discrete filaments are
exposed to a powerful electrostatic field. Electret filaments may
also be made by embedding excess charges into a highly insulating
dielectric material such as a (co)polymer or wax, e.g. by means of
an electron beam, a corona discharge, injection from an electron,
electric breakdown across a gap or a dielectric barrier, and the
like. Particularly suitable electret filaments are hydro-charged
filaments.
Optional Non-Melt-Spun Fiber Component
[0104] In additional exemplary embodiments, the nonwoven web
optionally further comprises a plurality of non-melt-spun
filaments. Thus, in exemplary embodiments, the nonwoven web may
additionally comprise discrete non-melt-spun filaments. Optionally,
the discrete non-melt-spun filaments are staple filaments.
Generally, the discrete non-melt-spun filaments act as filling
filaments, e.g. to reduce the cost or improve the properties of the
melt-spun nonwoven web.
[0105] Non-limiting examples of suitable non-melt-spun filling
filaments include single component synthetic filaments,
semi-synthetic filaments, polymeric filaments, metal filaments,
carbon filaments, ceramic filaments, and natural filaments.
Synthetic and/or semi-synthetic polymeric filaments include those
made of polyester (e.g., polyethylene terephthalate), nylon (e.g.,
hexamethylene adipamide, polycaprolactam), polypropylene, acrylic
(formed from a (co)polymer of acrylonitrile), rayon, cellulose
acetate, polyvinylidene chloride-vinyl chloride copolymers, vinyl
chloride-acrylonitrile copolymers, and the like.
[0106] Non-limiting examples of suitable metal filaments include
filaments made from any metal or metal alloy, for example, iron,
titanium, tungsten, platinum, copper, nickel, cobalt, and the
like.
[0107] Non-limiting examples of suitable carbon filaments include
graphite filaments, activated carbon filaments,
poly(acrylonitrile)-derived carbon filaments, and the like.
[0108] Non-limiting examples of suitable ceramic filaments include
any metal oxide, metal carbide, or metal nitride, including but not
limited to silicon oxide, aluminum oxide, zirconium oxide, silicon
carbide, tungsten carbide, silicon nitride, and the like.
[0109] Non-limiting examples of suitable natural filaments include
those of bamboo, cotton, wool, jute, agave, sisal, coconut,
soybean, hemp, and the like.
[0110] The filament component used may be virgin filaments or
recycled waste filaments, for example, recycled filaments reclaimed
from garment cuttings, carpet manufacturing, filament
manufacturing, textile processing, or the like.
[0111] The size and amount of discrete non-melt-spun filling
filaments, if included, used to form the nonwoven web, will
generally depend on the desired properties (i.e., loftiness,
openness, softness, drapability) of the nonwoven web 100 and the
desired loading of the chemically active particulate. Generally,
the larger the filament diameter, the larger the filament length,
and the presence of a crimp in the filaments will result in a more
open and lofty nonwoven article. Generally, small and shorter
filaments will result in a more compact nonwoven article.
Optional Particulate Component
[0112] In certain exemplary embodiments, the nonwoven web further
comprises a plurality of particulates. Exemplary nonwoven webs
according to the present disclosure may advantageously include a
plurality of chemically active particulates. The chemically active
particulates can be any discrete particulate, which is a solid at
room temperature, and which is capable of undergoing a chemical
interaction with an external fluid phase. Exemplary chemical
interactions include adsorption, absorption, chemical reaction,
catalysis of a chemical reaction, dissolution, and the like.
[0113] Additionally, in any of the foregoing exemplary embodiments,
the chemically active particulates may advantageously be selected
from sorbent particulates (e.g. adsorbent particulates, absorbent
particulates, and the like), desiccant particulates (e.g.
particulates comprising a hygroscopic substance such as, for
example, calcium chloride, calcium sulfate, and the like, that
induces or sustains a state of dryness in its local vicinity),
biocide particulates, microcapsules, and combinations thereof. In
any of the foregoing embodiments, the chemically active
particulates may be selected from activated carbon particulates,
activated alumina particulates, silica gel particulates anion
exchange resin particulates, cation exchange resin particulates,
molecular sieve particulates, diatomaceous earth particulates,
anti-microbial compound particulates, metal particulates, and
combinations thereof.
[0114] In one exemplary embodiment of a nonwoven web particularly
useful as a fluid filtration article, the chemically active
particulates are sorbent particulates. A variety of sorbent
particulates can be employed. Sorbent particulates include mineral
particulates, synthetic particulates, natural sorbent particulates
or a combination thereof. Desirably the sorbent particulates will
be capable of absorbing or adsorbing gases, aerosols, or liquids
expected to be present under the intended use conditions.
[0115] The sorbent particulates can be in any usable form including
beads, flakes, granules or agglomerates. Preferred sorbent
particulates include activated carbon; silica gel; activated
alumina and other metal oxides; metal particulates (e.g., silver
particulates) that can remove a component from a fluid by
adsorption or chemical reaction; particulate catalytic agents such
as hopcalite (which can catalyze the oxidation of carbon monoxide);
clay and other minerals treated with acidic solutions such as
acetic acid or alkaline solutions such as aqueous sodium hydroxide;
ion exchange resins; molecular sieves and other zeolites; biocides;
fungicides and virucides. Activated carbon and activated alumina
are presently particularly preferred sorbent particulates. Mixtures
of sorbent particulates can also be employed, e.g., to absorb
mixtures of gases, although in practice to deal with mixtures of
gases it may be better to fabricate a multilayer sheet article
employing separate sorbent particulates in the individual
layers.
[0116] In one exemplary embodiment of a nonwoven web particularly
useful as a gas filtration article, the chemically active sorbent
particulates are selected to be gas adsorbent or absorbent
particulates. For example, gas adsorbent particulates may include
activated carbon, charcoal, zeolites, molecular sieves, an acid gas
adsorbent, an arsenic reduction material, an iodinated resin, and
the like. For example, absorbent particulates may also include
naturally porous particulate materials such as diatomaceous earth,
clays, or synthetic particulate foams such as melamine, rubber,
urethane, polyester, polyethylene, silicones, and cellulose. The
absorbent particulates may also include superabsorbent particulates
such as sodium polyacrylates, carboxymethyl cellulose, or granular
polyvinyl alcohol.
[0117] In certain exemplary embodiments of a nonwoven web
particularly useful as a liquid filtration article, the sorbent
particulates comprise liquid an activated carbon, diatomaceous
earth, an ion exchange resin (e.g. an anion exchange resin, a
cation exchange resin, or combinations thereof), a molecular sieve,
a metal ion exchange sorbent, an activated alumina, an
antimicrobial compound, or combinations thereof. Certain exemplary
embodiments provide that the web has a sorbent particulate density
in the range of about 0.20 to about 0.5 g/cc.
[0118] Various sizes and amounts of sorbent chemically active
particulates may be used to create a nonwoven web. In one exemplary
embodiment, the sorbent particulates have a mean size greater than
1 mm in diameter. In another exemplary embodiment, the sorbent
particulates have a mean size less than 1 cm in diameter. In
further embodiments, a combination of particulate sizes can be
used. In one exemplary additional embodiment, the sorbent
particulates include a mixture of large particulates and small
particulates.
[0119] The desired sorbent particulate size can vary a great deal
and usually will be chosen based in part on the intended service
conditions. As a general guide, sorbent particulates particularly
useful for fluid filtration applications may vary in size from
about 0.001 to about 3000 .mu.m mean diameter. Generally, the
sorbent particulates are from about 0.01 to about 1500 .mu.m mean
diameter, more generally from about 0.02 to about 750 .mu.m mean
diameter, and most generally from about 0.05 to about 300 .mu.m
mean diameter.
[0120] In certain exemplary embodiments, the sorbent particulates
may comprise nano-particulates having a population mean diameter
less than 1 .mu.m. Porous nano-particulates may have the advantage
of providing high surface area for sorption of contaminants from a
fluid medium (e.g., absorption and/or adsorption). In such
exemplary embodiments using ultrafine or nano-particulates, it may
be preferred that the particulates are adhesively bonded to the
filaments using an adhesive, for example a hot melt adhesive,
and/or the application of heat to the melt-spun nonwoven web (i.e.,
thermal bonding).
[0121] Mixtures (e.g., bimodal mixtures) of sorbent particulates
having different size ranges can also be employed, although in
practice it may be better to fabricate a multilayer sheet article
employing larger sorbent particulates in an upstream layer and
smaller sorbent particulates in a downstream layer. At least 80
weight percent sorbent particulates, more generally at least 84
weight percent and most generally at least 90 weight percent
sorbent particulates are enmeshed in the web. Expressed in terms of
the web Basis Weight, the sorbent particulate loading level may for
example be at least about 500 gsm for relatively fine (e.g.
sub-micrometer-sized) sorbent particulates, and at least about
2,000 gsm for relatively coarse (e.g., micron-sized) sorbent
particulates.
[0122] In some exemplary embodiments, the chemically active
particulates are metal particulates. The metal particulates may be
used to create a polishing nonwoven web. The metal particulates may
be in the form of short filament or ribbon-like sections or may be
in the form of grain-like particulates. The metal particulates can
include any type of metal such as but not limited to silver (which
has antibacterial/antimicrobial properties), copper (which has
properties of an algaecide), or blends of one or more of chemically
active metals.
[0123] In other exemplary embodiments, the chemically active
particulates are solid biocides or antimicrobial agents. Examples
of solid biocide and antimicrobial agents include halogen
containing compounds such as sodium dichloroisocyanurate dihydrate,
benzalkonium chloride, halogenated dialkylhydantoins, and
triclosan.
[0124] In further exemplary embodiments, the chemically active
particulates are microcapsules. Microcapsules are described in U.S.
Pat. No. 3,516,941 (Matson), and include examples of the
microcapsules that can be used as the chemically active
particulates. The microcapsules may be loaded with solid or liquid
biocides or antimicrobial agents. One of the main qualities of a
microcapsule is that by means of mechanical stress the particulates
can be broken in order to release the material contained within
them. Therefore, during use of the nonwoven web, the microcapsules
will be broken due to the pressure exerted on the nonwoven web,
which will release the material contained within the
microcapsule.
[0125] In certain such exemplary embodiments, it may be
advantageous to use at least one particulate that has a surface
that can be made adhesive or "sticky" so as to bond together the
particulates to form a mesh or support nonwoven web for the
filament component. In this regard, useful particulates may
comprise a (co)polymer, for example, a thermoplastic (co)polymer,
which may be in the form of semi-continuous filaments. Suitable
polymers include polyolefins, particularly thermoplastic elastomers
(TPE's) (e.g., VISTAMAXX.TM., available from Exxon-Mobil Chemical
Company, Houston, Tex.). In further exemplary embodiments,
particulates comprising a TPE, particularly as a surface layer or
surface coating, may be preferred, as TPE's are generally somewhat
tacky, which may assist bonding together of the particulates to
form a three-dimensional network before addition of the filaments
to form the nonwoven web. In certain exemplary embodiments,
particulates comprising a VISTAMAXX.TM. TPE may offer improved
resistance to harsh chemical environments, particularly at low pH
(e.g., pH no greater than about 3) and high pH (e.g., pH of at
least about 9) and in organic solvents.
[0126] Any suitable size or shape of particulate material may be
selected. Suitable particulates may have a variety of physical
forms (e.g., solid particulates, porous particulates, hollow
bubbles, agglomerates, semi-continuous filaments, staple filaments,
flakes, and the like); shapes (e.g., spherical, elliptical,
polygonal, needle-like, and the like); shape uniformities (e.g.,
monodisperse, substantially uniform, non-uniform or irregular, and
the like); composition (e.g. inorganic particulates, organic
particulates, or combination thereof); and size (e.g.,
sub-micrometer-sized, micro-sized, and the like).
[0127] With particular reference to particulate size, in some
exemplary embodiments, it may be desirable to control the size of a
population of the particulates. In certain exemplary embodiments,
particulates are physically entrained or trapped in the filament
nonwoven web. In such embodiments, the population of particulates
is generally selected to have a mean diameter of at least 50 .mu.m,
more generally at least 75 .mu.m, still more generally at least 100
.mu.m.
[0128] In other exemplary embodiments, it may be preferred to use
finer particulates that are adhesively bonded to the filaments
using an adhesive, for example a hot melt adhesive, and/or the
application of heat to one or both of thermoplastic particulates or
thermoplastic filaments (i.e., thermal bonding). In such
embodiments, it is generally preferred that the particulates have a
mean diameter of at least 25 .mu.m, more generally at least 30
.mu.m, most generally at least 40 .mu.m. In some exemplary
embodiments, the chemically active particulates have a mean size
less than 1 cm in diameter. In other embodiments, the chemically
active particulates have a mean size of less than 1 mm, more
generally less than 25 micrometers, even more generally less than
10 micrometers.
[0129] However, in other exemplary embodiments in which both an
adhesive and thermal bonding are used to adhere the particulates to
the filaments, the particulates may comprise a population of
sub-micrometer-sized particulates having a population mean diameter
of less than one micrometer (.mu.m), more generally less than about
0.9 .mu.m, even more generally less than about 0.5 .mu.m, most
generally less than about 0.25 .mu.m. Such sub-micrometer-sized
particulates may be particularly useful in applications where high
surface area and/or high absorbency and/or adsorbent capacity is
desired. In further exemplary embodiments, the population of
sub-micrometer-sized particulates has a population mean diameter of
at least 0.001 .mu.m, more generally at least about 0.01 .mu.m,
most generally at least about 0.1 .mu.m, most generally at least
about 0.2 .mu.m.
[0130] In further exemplary embodiments, the particulates comprise
a population of micro-sized particulates having a population mean
diameter of at most about 2,000 .mu.m, more generally at most about
1,000 .mu.m, most generally at most about 500 .mu.m. In other
exemplary embodiments, the particulates comprise a population of
micro-sized particulates having a population mean diameter of at
most about 10 .mu.m, more generally at most about 5 .mu.m, even
more generally at most about 2 .mu.m (e.g., ultrafine
micro-filaments).
[0131] Multiple types of particulates may also be used within a
single finished web. Using multiple types of particulates, it may
be possible to generate continuous particulate webs even if one of
the particulate types does not bond with other particulates of the
same type. An example of this type of system would be one where two
types are particulates are used, one that bonds the particulates
together (e.g., a semi-continuous polymeric filament particulate)
and another that acts as an active particulate for the desired
purpose of the web (e.g., a sorbent particulate such as activated
carbon). Such exemplary embodiments may be particularly useful for
fluid filtration applications.
[0132] Depending, for example, on the density of the chemically
active particulate, size of the chemically active particulate,
and/or desired attributes of the final nonwoven web article, a
variety of different loadings of the chemically active particulates
may be used relative to the total weight of the fibrous web. In one
embodiment, the chemically active particulates comprise less than
90% wt. of the total nonwoven article weight. In one embodiment,
the chemically active particulates comprise at least 10% wt. of the
total nonwoven article weight.
[0133] In any of the foregoing embodiments, the chemically active
particulates may be advantageously distributed throughout the
entire thickness of the nonwoven web. However, in some of the
foregoing embodiments, the chemically active particulates are
preferentially distributed substantially on a major surface of the
nonwoven web.
[0134] Furthermore, it is to be understood that any combination of
one or more of the above described chemically active particulates
may be used to form nonwoven webs according to the present
disclosure.
Processes for Forming a Semi-Continuous Filament
[0135] In another aspect, the present disclosure describes a
process for making a nonwoven web, comprising heating a mixture of
about 50% w/w to about 99% w/w of a crystalline polyolefin
(co)polymer, and from about 1% w/w to about 40% w/w of a
hydrocarbon tackifier resin to at least a Melting Temperature of
the mixture to form a molten mixture, extruding the molten mixture
through at least one orifice to form at least one semi-continuous
filament, attenuating the at least one semi-continuous filament to
draw and molecularly orient the at least one semi-continuous
filament, and cooling the at least one semi-continuous filament to
a temperature below the Melting Temperature of the molten mixture
to form a melt-spun nonwoven web, wherein the at least one
semi-continuous (co)polymeric filament exhibits molecular
orientation, and further wherein at least one of the crystalline
polyolefin (co)polymer or the nonwoven web exhibits a Heat of
Fusion measured using Differential Scanning Calorimetry of greater
than 50 Joules/g.
[0136] In further such exemplary embodiments, the at least one
semi-continuous filament comprises a plurality of semi-continuous
filaments, and the process further includes collecting the
plurality of semi-continuous filaments as the nonwoven web on a
collector. Preferably, the plurality of semi-continuous filaments
is comprised of melt-spun filaments. In the melt-spinning process,
the crystalline polyolefin (co)polymer/hydrocarbon resin tackifier
mixture is melted to form a molten mixture, which is then extruded
through one or more orifices of a melt-spinning die.
[0137] Preferably the melt-spun filaments are subjected to a
filament bonding step before, during, or after collection, thereby
producing a spun-bond nonwoven web. In certain exemplary
embodiments, bonding comprises one or more of autogenous thermal
bonding, non-autogenous thermal bonding, through air bonding, and
ultrasonic bonding.
[0138] Suitable melt-spinning and spun-bonding processes,
attenuation methods and apparatus, and bonding methods and
apparatus (including autogenous bonding methods) are described in
U.S. Pat. Nos. 6,607,624 (Berrigan et al.) and 7,807,591 B2 (Fox et
al.), the entire disclosures of which are incorporated herein by
reference in their entireties.
[0139] In some exemplary embodiments, the process further includes
at least one of addition of a plurality of staple filaments to the
plurality of semi-continuous filaments, or addition of a plurality
of particulates to the plurality of semi-continuous filaments.
[0140] In further embodiments, the process further includes
processing the collected nonwoven web using a process selected from
bonding, electret charging, embossing, needle-punching, needle
tacking, hydroentangling, or a combination thereof.
[0141] In any of the foregoing processes, the melt-spinning should
be performed within a range of temperatures hot enough to enable
the crystalline polyolefin (co)polymer/hydrocarbon resin tackifier
mixture to be melt-spun but not so hot as to cause unacceptable
deterioration of the crystalline polyolefin (co)polymer/hydrocarbon
resin tackifier mixture. For example, the melt-spinning can be
performed at a temperature that causes the molten mixture of the
crystalline polyolefin (co)polymer and hydrocarbon resin tackifier
to reach a processing temperature at least 40-50.degree. C. above
the melting temperature.
[0142] Preferably, the processing temperature of the molten mixture
is selected to be 200.degree. C., 225.degree. C., 250.degree. C.,
260.degree. C., 270.degree. C., 280.degree. C., or even at least
290.degree. C.; to less than or equal to about 360.degree. C.,
350.degree. C., 340.degree. C., 330.degree. C., 320.degree. C.,
310.degree. C., or even 300.degree. C.
Processes for Forming Composite Nonwoven Webs
[0143] In some such exemplary embodiments, the process further
includes at least one of addition of a plurality of staple
filaments to the plurality of discrete, semi-continuous filaments,
or addition of a plurality of particulates to the plurality of
discrete, semi-continuous filaments, to form a composite nonwoven
web.
[0144] In some exemplary embodiments, the method of making a
composite nonwoven web comprises combining the microfilament or
coarse microfilament population with the fine microfilament
population, the ultrafine microfilament population, or the
sub-micrometer filament population by mixing filament streams,
hydroentangling, wet forming, plexifilament formation, or a
combination thereof.
[0145] In combining the microfilament or coarse microfilament
population with the fine, ultrafine or sub-micrometer filament
populations, multiple streams of one or both types of filaments may
be used, and the streams may be combined in any order. In this
manner, nonwoven composite fibrous webs may be formed exhibiting
various desired concentration gradients and/or layered
structures.
[0146] For example, in certain exemplary embodiments, the
population of fine, ultrafine or sub-micrometer filaments may be
combined with the population of microfilaments or coarse
microfilaments to form an inhomogenous mixture of filaments. In
certain exemplary embodiments, at least a portion of the population
of fine, ultrafine or sub-micrometer filaments is intermixed with
at least a portion of the population of microfilaments. In other
exemplary embodiments, the population of fine, ultrafine or
sub-micrometer filaments may be formed as an overlayer on an
underlayer comprising the population of microfilaments. In certain
other exemplary embodiments, the population of microfilaments may
be formed as an overlayer on an underlayer comprising the
population of fine, ultrafine or sub-micrometer filaments.
Optional Particulate Loading Processes
[0147] In many applications, substantially uniform distribution of
particles throughout the web is desired. There may also be
instances where non-uniform distributions may be advantageous. In
certain exemplary embodiments, a particulate density gradient may
advantageously be created within the composite nonwoven web. For
example, gradients through the depth of the web may create changes
to the pore size distribution that could be used for depth
filtration. Webs with a surface loading of particles could be
formed into a filter where the fluid is exposed to the particles
early in the flow path and the balance of the web provides a
support structure and means to prevent sloughing of the particles.
The flow path could also be reversed so the web can act as a
pre-filter to remove some contaminants prior to the fluid reaching
the active surface of the particles.
[0148] Various methods are known for adding a stream of
particulates to a nonwoven filament stream. Suitable methods are
described in U.S. Pat. Nos. 4,118,531 (Hauser), 6,872,311 (Koslow),
and 6,494,974 (Riddell); and in U.S. Patent Application Publication
Nos. 2005/0266760 (Chhabra and Isele), 2005/0287891 (Park) and
2006/0096911 (Brey et al.).
[0149] In other exemplary embodiments, the optional particulates
could be added to a nonwoven filament stream by air laying a
filament web, adding particulates to the filament web (e.g., by
passing the web through a fluidized bed of particulates),
optionally with post heating of the particulate-loaded web to bond
the particulates to the filaments. Alternatively, a pre-formed web
could be sprayed with a pre-formed dispersion of particulates in a
volatile fluid (e.g. an organic solvent, or even water), optionally
with post heating of the particulate-loaded web to remove the
volatile fluid and bond the particulates to the filaments.
[0150] In further exemplary embodiments, the process further
includes collecting the plurality of discrete, semi-continuous
filaments as the nonwoven web on a collector. In certain such
exemplary embodiments, the composite nonwoven web may be formed by
depositing the population of fine, ultrafine or sub-micrometer
filaments directly onto a collector surface, or onto an optional
support layer on the collector surface, the support layer
optionally comprising microfilaments, so as to form a population of
fine, ultrafine or sub-micrometer filaments on the porous support
layer.
[0151] The process may include a step wherein the optional support
layer, which optionally may comprise polymeric microfilaments, is
passed through a filament stream of fine, ultrafine or
sub-micrometer filaments. While passing through the filament
stream, fine, ultrafine or sub-micrometer filaments may be
deposited onto the support layer so as to be temporarily or
permanently bonded to the support layer. When the filaments are
deposited onto the support layer, the filaments may optionally bond
to one another, and may further harden while on the support
layer.
[0152] In certain exemplary embodiments, the fine, ultrafine or
sub-micrometer filament population is combined with an optional
porous support layer that comprises at least a portion of the
coarse microfilament population. In some exemplary embodiments, the
microfilaments forming the porous support layer are compositionally
the same as the population of microfilaments that forms the first
layer. In other presently preferred embodiments, the fine,
ultrafine or sub-micrometer filament population is combined with an
optional porous support layer and subsequently combined with at
least a portion of the coarse microfilament population. In certain
other presently preferred embodiments, the porous support layer
adjoins the second layer opposite the first layer.
[0153] In other exemplary embodiments, the porous support layer
comprises a nonwoven fabric, a woven fabric, a knitted fabric, a
foam layer, a screen, a porous film, a perforated film, an array of
filaments, or a combination thereof. In some exemplary embodiments,
the porous support layer comprises a thermoplastic mesh.
Optional Processing Steps
[0154] In some embodiments, the process further includes processing
the collected nonwoven web using a process selected from bonding
(e.g., autogenous bonding, through-air bonding, calendering, and
the like), electret charging, embossing, needle-punching, needle
tacking, hydroentangling, or a combination thereof.
Optional Bonding Processes
[0155] Depending on the condition of the filaments and the relative
proportion of microfilaments and sub-micrometer filaments, some
bonding may occur between the filaments themselves (e.g.,
autogenous bonding) and between the filaments and any optional
particulates, before or during collection. "Bonding the filaments
together" means adhering the filaments together firmly without an
additional adhesive material, so that the filaments generally do
not separate when the web is subjected to normal handling).
[0156] However, further bonding between the filaments themselves
and between the filaments and any optional filaments or
particulates in the collected web may be desirable to provide a
matrix of desired coherency, making the web more handle-able and
better able to hold any sub-micrometer filaments within the matrix
("bonding" filaments themselves means adhering the filaments
together firmly, so they generally do not separate when the web is
subjected to normal handling).
[0157] Bonding may be achieved, for example, using thermal bonding,
adhesive bonding, powdered binder, hydroentangling,
needle-punching, calendering, or a combination thereof.
Conventional bonding techniques using heat and pressure applied in
a point-bonding process or by smooth calender rolls can be used,
though such processes may cause undesired deformation of filaments
or excessive compaction of the web. A presently-preferred technique
for bonding the filaments is through-air bonding as disclosed in
U.S. Pat. Pub. No. 2008/0038976 (Berrigan et al.).
[0158] In some embodiments where light autogenous bonding provided
by through-air bonding may not provide the desired web strength for
peel or shear performance, it may be useful to incorporate a
secondary or supplemental bonding step, for example, point bonding
or calendering, after removal of the nonwoven web from the
collector surface. Virtually any bonding technique may be used to
achieve supplemental bonding, for example, application of one or
more adhesives to one or more surfaces to be bonded, ultrasonic
welding, or other thermal bonding methods able to form localized
bond patterns, as known to those skilled in the art. Such
supplemental bonding may make the web more easily handled and
better able to hold its shape.
Optional Electret Charging Processes
[0159] In some particular embodiments, the melt-spun filaments may
be advantageously electrostatically charged. Thus, in certain
exemplary embodiments, the melt-spun filaments may be subjected to
an electret charging process. An exemplary electret charging
process is hydro-charging. Hydro-charging of filaments may be
carried out using a variety of techniques including impinging,
soaking or condensing a polar fluid onto the filament, followed by
drying, so that the filament becomes charged. Representative
patents describing hydro-charging include U.S. Pat. Nos. 5,496,507;
5,908,598; 6,375,886 B1; 6,406,657 B1; 6,454,986 and 6,743,464 B1.
Preferably water is employed as the polar hydro-charging liquid,
and the media preferably is exposed to the polar hydro-charging
liquid using jets of the liquid or a stream of liquid droplets
provided by any suitable spray means.
[0160] Devices useful for hydraulically entangling filaments are
generally useful for carrying out hydro-charging, although the
operation is carried out at lower pressures in hydro-charging than
generally used in hydro-entangling. U.S. Pat. No. 5,496,507
describes an exemplary apparatus in which jets of water or a stream
of water droplets are impinged upon the filaments in web form at a
pressure sufficient to provide the subsequently-dried media with a
filtration-enhancing electret charge.
[0161] The pressure necessary to achieve optimum results may vary
depending on the type of sprayer used, the type of (co)polymer from
which the filament is formed, the thickness and density of the web,
and whether pretreatment such as corona charging was carried out
before hydro-charging. Generally, pressures in the range of about
69 kPa to about 3450 kPa are suitable. Preferably, the water used
to provide the water droplets is relatively pure. Distilled or
deionized water is preferable to tap water.
[0162] The electret filaments may be subjected to other charging
techniques in addition to or alternatively to hydro-charging,
including electrostatic charging (e.g., as described in U.S. Pat.
Nos. 4,215,682, 5,401,446 and 6,119,691), tribo-charging (e.g., as
described in U.S. Pat. No. 4,798,850) or plasma fluorination (e.g.,
as described in U.S. Pat. No. 6,397,458 B1). Corona charging
followed by hydro-charging and plasma fluorination followed by
hydro-charging are particularly suitable charging techniques used
in combination.
Optional Post-Collection Processing
[0163] Various processes conventionally used as adjuncts to
filament-forming processes may be used in connection with filaments
as they exit from one or more orifices of the belt blowing die.
Such processes include spraying of finishes, adhesives or other
materials onto the filaments, application of an electrostatic
charge to the filaments, application of water mists to the
filaments, and the like. In addition, various materials may be
added to a collected web, including bonding agents, adhesives,
finishes, and other webs or films. For example, prior to
collection, extruded filaments or filaments may be subjected to a
number of additional processing steps, e.g., further drawing,
spraying, and the like. Various fluids may also be advantageously
applied to the filaments before or during collection, including
water sprayed onto the filaments, e.g., heated water or steam to
heat the filaments, or cold water to quench the filaments.
[0164] After collection, the collected mass may additionally or
alternatively be wound into a storage roll for later processing if
desired. Generally, once the collected melt-spun nonwoven web has
been collected, it may be conveyed to other apparatus such as
calenders, embossing stations, laminators, cutters and the like; or
it may be passed through drive rolls and wound into a storage
roll.
[0165] Thus, in addition to the foregoing methods of making and
optionally bonding or electret charging a nonwoven web, one or more
of the following process steps may optionally be carried out on the
web once formed:
[0166] (1) advancing the composite nonwoven web along a process
pathway toward further processing operations;
[0167] (2) bringing one or more additional layers into contact with
an outer surface of the sub-micrometer filament component, the
microfilament component, and/or the optional support layer;
[0168] (3) calendering the composite nonwoven web;
[0169] (4) coating the composite nonwoven web with a surface
treatment or other composition (e.g., a fire-retardant composition,
an adhesive composition, or a print layer);
[0170] (5) attaching the composite nonwoven web to a cardboard or
plastic tube;
[0171] (6) winding-up the composite nonwoven web in the form of a
roll;
[0172] (7) slitting the composite nonwoven web to form two or more
slit rolls and/or a plurality of slit sheets;
[0173] (8) placing the composite nonwoven web in a mold and molding
the composite nonwoven web into a new shape; and
[0174] (9) applying a release liner over an exposed optional
pressure-sensitive adhesive layer, when present.
Articles Incorporating Nonwoven Melt-Spun (Spun-Bond) Fibrous
Webs
[0175] Nonwoven fibrous webs can be made using the foregoing
processes. In some exemplary embodiments, the nonwoven web or
composite web takes the form of a mat, web, sheet, a scrim, or a
combination thereof.
[0176] In some particular exemplary embodiments, the nonwoven web
or composite web may advantageously include charged melt-spun
filaments, e.g., electret filaments. In certain exemplary
embodiments, the melt-spun nonwoven web or web is porous. In some
additional exemplary embodiments, the nonwoven web or composite web
may advantageously be self-supporting. In further exemplary
embodiments, the melt-spun nonwoven web or composite nonwoven web
advantageously may be pleated, e.g., to form a filtration medium,
such as a liquid (e.g., water) or gas (e.g., air) filter, a
heating, ventilation or air conditioning (HVAC) filter, or a
respirator for personal protection. For example, U.S. Pat. No.
6,740,137 discloses nonwoven webs used in a collapsible pleated
filter element.
[0177] Webs of the present disclosure may be used by themselves,
e.g., for filtration media, decorative fabric, or a protective or
cover stock. Or they may be used in combination with other webs or
structures, e.g., as a support for other fibrous layers deposited
or laminated onto the web, as in a multilayer filtration media, or
a substrate onto which a membrane may be cast. They may be
processed after preparation as by passing them through smooth
calendering rolls to form a smooth-surfaced web, or through shaping
apparatus to form them into three-dimensional shapes.
[0178] A nonwoven web or composite web of the present disclosure
can further comprise at least one or a plurality of other types of
filaments (not shown) such as, for example, staple or otherwise
semi-continuous filaments, melt spun continuous filaments or a
combination thereof. The present exemplary fibrous webs can be
formed, for example, into a non-woven web that can be wound about a
tube or other core to form a roll, and either stored for subsequent
processing or transferred directly to a further processing step.
The web may also be cut into individual sheets or mats directly
after the web is manufactured or sometime thereafter.
[0179] The melt-spun nonwoven webs or composite webs can be used to
make any suitable article such as, for example, a thermal
insulation article, an acoustic insulation article, a fluid
filtration article, a wipe, a surgical drape, a wound dressing, a
garment, a respirator, or a combination thereof. The thermal or
acoustic insulation articles may be used as an insulation component
for vehicles (e.g., trains, airplanes, automobiles and boats).
Other articles such as, for example, bedding, shelters, tents,
insulation, insulating articles, liquid and gas filters, wipes,
garments, garment components, personal protective equipment,
respirators, and the like, can also be made using melt-spun
nonwoven webs of the present disclosure.
[0180] Flexible, drape-able and compact nonwoven webs may be
preferred for certain applications, for examples as furnace filters
or gas filtration respirators. Such nonwoven webs typically have a
density greater than 75 kg/m.sup.3 and typically greater than 100
kg/m.sup.3 or even 120 kg/m.sup.3. However, open, lofty nonwoven
webs suitable for use in certain fluid filtration applications
generally have a maximum density of 60 kg/m.sup.3.
[0181] Thus, in certain exemplary embodiments, the nonwoven webs
exhibit a Basis Weight of from 1 gsm to 400 gsm, more preferably
from 1 gsm to 200 gsm, even more preferably from 1 gsm to 100 gsm,
or even 1 gsm to about 50 gsm.
[0182] Certain presently-preferred nonwoven webs according to the
present disclosure may have a Solidity less than 50%, 340%, 30%,
20%, or more preferably less than 15%, even more preferably less
than 10%.
[0183] The operation of the processes of the present disclosure to
produce nonwoven webs as described herein, will be further
described with regard to the following detailed examples. These
examples are offered to further illustrate the various specific and
preferred embodiments and techniques. It should be understood,
however, that many variations and modifications may be made while
remaining within the scope of the present disclosure.
EXAMPLES
[0184] These Examples are merely for illustrative purposes and are
not meant to be overly limiting on the scope of the appended
claims. Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the present disclosure are
approximations, the numerical values set forth in the specific
examples are reported as precisely as possible. Any numerical
value, however, inherently contains certain errors necessarily
resulting from the standard deviation found in their respective
testing measurements. At the very least, and not as an attempt to
limit the application of the doctrine of equivalents to the scope
of the claims, each numerical parameter should at least be
construed in light of the number of reported significant digits and
by applying ordinary rounding techniques.
Summary of Materials
[0185] Unless otherwise noted, all parts, percentages, ratios, etc.
in the Examples and the rest of the specification are by
weight.
[0186] Mono-component polypropylene and blends of Polypropylene and
OPPERA.TM. resins were used to prepare semi-continuous filaments
comprising from about 50% w/w to about 99% w/w of at least one
crystalline polyolefin (co)polymer, and from about 1% w/w to about
40% w/w of at least one hydrocarbon tackifier resin, as well as
nonwoven webs including such semi-continuous filaments.
[0187] The crystalline polyolefin (co)polymer was selected as Total
3860 polypropylene (available from Total Petrochemicals and
Refining U.S.A., Houston, Tex.).
[0188] The hydrocarbon tackifier resin was selected as OPPERA.TM.
PR100A (available from Exxon-Mobil Chemical Co., Spring, Tex.)
[0189] Solvents and other reagents used may be obtained from
Sigma-Aldrich Chemical Company (Milwaukee, Wis.).
Test Methods
[0190] The following test methods have been used in evaluating some
of the Examples of the present disclosure.
Optical Microscopy Test of Actual Filament Diameter
[0191] The Actual Filament Diameter (AFD) was determined using an
optical microscope equipped with a calibrated reticle. The AFD is
the average (mean) number diameter determined from measurements
taken on 20 individual filaments observed in the nonwoven web
sample when positioned under the microscope objective at a focal
point of the objective lens.
Effective Filament Diameter
[0192] The Effective Filament Diameter (EFD) was determined using
an air flow rate of 32 L/min (corresponding to a face velocity of
5.3 cm/sec), using the method set forth in Davies, C. N., "The
Separation of Airborne Dust and Particles," Institution of
Mechanical Engineers, London, Proceedings IB, 1952.
Differential Scanning Calorimetry (Melting Temperature and Heat of
Fusion)
[0193] Differential Scanning Calorimetry (DSC) was used to
determine the Melting Temperature and Heat of Fusion of the
crystalline polyolefin, the mixture of the crystalline polyolefin
with the hydrocarbon tackifier resin, and the nonwoven webs
produced from the mixture.
[0194] The DSC analysis was carried out using a Model DSC Q2000
available from Ta Instruments Co. (New Castle, Del.). Approximately
1.5 mg to 10 mg of the crystalline polyolefin, the mixture of the
crystalline polyolefin with the hydrocarbon tackifier resin, or the
nonwoven web produced from the mixture, was loaded and sealed in an
aluminum pan and placed in the DSC Q2000 apparatus.
[0195] DSC measurements on each sample was carried out using the
following sequential
[0196] Heating-Cooling-Heating cycle. Each sample was initially
heated from -20.degree. C. to 250.degree. C. (or at least
30.degree. C. above the Melting Temperature of the sample) at a
rate of 10.degree. C./minute. Each sample was then held for 1
minute at 250.degree. C., and then subsequently cooled down to
-20.degree. C. (or at least 50.degree. C. below the crystallization
temperature of the sample) at a rate of 20.degree. C./min. Each
sample was then held for 1 minute at -20.degree. C. and then
subsequently heated from -20.degree. C. to 200.degree. C. at
10.degree. C./min.
[0197] The temperature corresponding to the highest-temperature
endothermic peak was reported as the Melting Temperature (.degree.
C.), and the area under the same highest-temperature endothermic
peak was reported as the Heat of Fusion.
Tensile Strength Test
[0198] The tensile properties of webs in the Examples were measured
by pulling to failure a 1 inch by 6-inch sample (2.5 cm by 15.2
cm). The thickness of the nonwoven web samples was about 0.15 cm.
The Tensile Strength Test was carried out using a commercially
available tensile test apparatus designated as Instron Model 5544
(available from Instron Company, Canton, Mass.). The gauge length
was 4 inches (10.2 cm), and the cross-head speed was 308
millimeters/per minute. The Maximum Tensile Load (in Newtons) was
determined in the machine direction of the nonwoven web.
Stiffness Test
[0199] Stiffness of the nonwoven webs in the machine direction was
measured with a Gurley Bending Resistance Tester Model 4171E
(available from Gurley Precision Instruments, Inc., Troy, N.Y.).
Five 1.5 inch (about 3.9 cm).times.2 inch (about 5.1 cm) coupons
were cut from the center lane of each nonwoven web with the 1.5
inch (about 3.9 cm) length corresponding to the machine direction
of the web. Each coupon was then clamped in the Gurley Bending
Resistance Tester, and the Tester motor was operated in each of two
directions such that the Tester pendulum swung across the coupon
until full deflection of the pendulum was achieved. Pendulum
weights and positions were selected such that deflection of the
pendulum was kept between 1 inch (2.54 cm) and 6 inches (about 15.2
cm) for any given sample. Results of nonwoven web Stiffness are
reported for each nonwoven web as the average of the force (in mg)
measured for each coupon from both directions.
Examples of Melt-Spun (Spun-Bond) Webs and Composite Melt-Spun
(Spun-Bond) Webs
[0200] The following Examples illustrate the preparation of various
melt-spun (spun-bond) nonwoven webs prepared according to the
processes described in the present disclosure. For the Comparative
Examples and Examples, melt-spun (spun-bond) filaments and nonwoven
webs including such filaments were prepared using an apparatus as
depicted in FIG. 1 of U.S. Pat. Nos. 6,607,624 (Berrigan et al.),
and using the process as described generally by Berrigan et al.
However, instead of two single-screw extruders (reference numeral
12 as shown in FIG. 1), a single 25 mm Berstorff twin-screw
extruder (available from Krauss-Maffei Group, U.S.A., Florence,
Ky.) was used to heat and extrude the molten (co)polymer mixture
through the die.
Comparative Example C-1
[0201] Mono-component semi-continuous filaments and melt-spun
(spun-bond) nonwoven webs including such filaments were prepared
using Total 3860 polypropylene. The semi-continuous filaments were
formed from a multi-orifice die that was 18'' (about 45.7 cm) wide
and had approximately 1800 orifices. The semi-continuous filaments
were extruded at 0.04 grams/orifice/minute (ghm) at a temperature
of 245.degree. C. The air attenuator was kept at 3 psig (about
20,684 Pa), which led to the calculated filament spinning speed of
837 m/min. The melt-spun (spun-bond) nonwoven web was made at a
target basis weight of .about.120 gsm.
Comparative Example C-2
[0202] The melt-spun (spun-bond) web was made using the conditions
which described in Comparative Example C-1, except the air pressure
of the attenuator was increased to 7 psig (about 48,263 Pa). This
was the point where considerable filament breakage was observed.
The filament size of the melt-spun (spun-bond) media obtained was
6.2 .mu.m at a calculated filament spinning speed of 1464
m/min.
Example 1
[0203] The melt-spun (spun-bond) media was made as described in
Comparative Example C-2 except the 25 mm Berstorff twin-screw
extruder was used with two loss in weight feeders to control the
feeding of the Total PP 3860 and OPPERA PR100A resins to the
extruder barrel and a melt pump to control the polymer melt flow to
a die. The web was made using the blend ratio of (90/10) in between
PP 3860 and OPPERA.TM. PR 100A. The extruder temperature was at
about 245.degree. C. and it delivered the blend melt stream to the
melt-spun (spun-bond) die maintained at 245.degree. C. The gear
pump was adjusted so that a 0.04 grams/orifice/minute (ghm) polymer
throughput rate was maintained at the melt-spun (spun-bond)
die.
[0204] The resulting web was collected at the collector and had a
basis weight of approximately 121 g/m.sup.2. The air attenuator was
kept at 3 psig (about 20,684 Pa) which led to a filament size of
8.3 microns at a calculated filament spinning speed of 817
m/min.
Example 2
[0205] The melt-spun (spun-bond) web was made using the conditions
which described in Example 1, except the air pressure of the
attenuator was increased to 18 psig (124,106 Pa). At this point no
significant filament breakage occurred. The filament size of the
melt-spun (spun-bond) media obtained was 4.6 .mu.m at a calculated
filament spinning speed of 2660 m/min.
Example 3
[0206] The melt-spun (spun-bond) web was made using the conditions
which described in Example 2, except the flow rate of the blend was
increased from 0.04 to 0.11 grams/orifice/minute. At this point no
filament breakage was observed. The filament size of the melt-spun
(spun-bond) media obtained was 7 .mu.m at a calculated filament
spinning speed of 3159 m/min.
Example 4
[0207] The melt-spun (spun-bond) web was made using the conditions
which described in Example 1, except the ratio of PP 3860 and
OPPERA.TM. PR 100A was increased to 80/20 w/w. The filament size of
the melt-spun (spun-bond) media obtained was 7.3 .mu.m at a
calculated filament spinning speed of 1056 m/min.
Example 5
[0208] The melt-spun (spun-bond) web was made using the conditions
which described in Example 4, except the air pressure of the
attenuator was increased to 7 psig (about 48,263 Pa). The filament
size of the melt-spun (spun-bond) media obtained was 6.6 .mu.m at a
calculated filament spinning speed of 1292 m/min.
Example 6
[0209] The melt-spun (spun-bond) web was made using the conditions
which described in Example 5, except the air pressure of the
attenuator was increased to 16 psig (110,316 Pa). The filament size
of the melt-spun (spun-bond) media obtained was 5.2 .mu.m at a
calculated filament spinning speed of 2081 m/min.
Example 7
[0210] The melt-spun (spun-bond) web was made using the conditions
which described in Example 6, except the flow rate of the blend was
increased from 0.04 to 0.11 grams/orifice/minute and the air
pressure of the attenuator was increased to 18 psig (124,106 Pa).
The filament size of the melt-spun (spun-bond) media obtained was
7.5 .mu.m at a calculated filament spinning speed of 2751
m/min.
Example 8
[0211] The melt-spun (spun-bond) web was made using the conditions
which described in Example 7, except the air pressure of the
attenuator was increased to 40 psig (275,790 Pa). The filament size
of the melt-spun (spun-bond) media obtained was 6.1 .mu.m at a
calculated filament spinning speed of 4159 m/min.
[0212] The melt-spinning process conditions for Comparative
Examples 1-2 and Examples 1-8 are summarized in Table 1, and the
Melt-spun (Spun-bond) Nonwoven Web Properties for Comparative
Examples 1-2 and Examples 1-8 are summarized in Table 2. Table 3
summarizes the DSC-measured Melting Temperatures and Heats of
Fusion for each of the of melt-spun (spun-bond) nonwoven webs
produced in Comparative Examples 1-2 and Examples 1-8.
TABLE-US-00001 TABLE 1 Melt-spinning Process Conditions for
Comparative Examples 1-2 and Examples 1-8 Filament .DELTA.P
Attenuator Spinning Rate (at 85 L/m) Pressure Speed Example #
Material (lb/hr) (mm H.sub.20) (psig) (m/min) C-1 PP 3860 10 6.3 3
837 C-2 PP 3860 10 8.42 7 1464 1 PP 3860 + 10 4.66 3 817 10% OPPERA
2 PP 3860 + 10 8.8 18 2660 10% OPPERA 3 PP 3860 + 25 5.8 18 3159
10% OPPERA 4 PP 3860 + 10 4.13 3 1056 20% OPPERA 5 PP 3860 + 10
7.07 7 1292 20% OPPERA 6 PP 3860 + 10 7.95 16 2081 20% OPPERA 7 PP
3860 + 25 4.9 18 2751 20% OPPERA 8 PP 3860 + 25 3.93 40 4159 20%
OPPERA
TABLE-US-00002 TABLE 2 Melt-spun (Spun-bond) Nonwoven Web
Properties for Comparative Examples 1-2 and Examples 1-8 Base
Stiffness/ Tensile Strength Weight Thickness EFD AFD Stiffness
Thickness MD CD Example # Material (gsm) (mils) (.mu.m) (.mu.m)
(mg) (g/m) (N) (N) C-1 PP 3860 119 48 11.0 8.2 679.3 3.7 55.7 24.8
C-2 PP 3860 123 55.5 9.3 6.2 557 2.6 73.0 31.0 1 PP 3860 + 121 49
12.9 8.3 885.8 4.6 46.4 20.4 10% OPPERA 2 PP 3860 + 117 40 9.8 4.6
1316.5 8.4 143.6 39.8 10% OPPERA 3 PP 3860 + 122 37 13 7 1474.1
10.1 120.2 56.4 10% OPPERA 4 PP 3860 + 120 48.5 13.7 7.3 1514 7.9
70.4 35.2 20% OPPERA 5 PP 3860 + 122 50 10.5 6.6 1305.4 6.6 91.0
34.1 20% OPPERA 6 PP 3860 + 116 42 10.1 5.2 1292 7.8 124.8 45.2 20%
OPPERA 7 PP 3860 + 124 41 13.8 7.5 1758.2 10.9 109.7 43.4 20%
OPPERA 8 PP 3860 + 120 47 14.2 6.1 2091.2 11.3 147.4 69.6 20%
OPPERA
TABLE-US-00003 TABLE 3 Melting Temperature and Heat of Fusion of
melt-spun (spun-bond) webs described in Comparative Examples 1-2
and Examples 1-8 Melting Example Heat of Fusion Temperature Number
Material (J/g) (.degree. C.) C-1 PP 3860 102.6 162.8 C-2 PP 3860
103.6 163.2 1 PP 3860 + 96.3 160.8 10% OPPERA 2 PP 3860 + 90.1
163.3 10% OPPERA 3 PP 3860 + 88.5 163.5 10% OPPERA 4 PP 3860 + 97.7
159.7 20% OPPERA 5 PP 3860 + 84.4 160.4 20% OPPERA 6 PP 3860 + 83.4
161.1 20% OPPERA 7 PP 3860 + 81.1 161.8 20% OPPERA 8 PP 3860 + 87.3
162.3 20% OPPERA
[0213] The data provided in Tables 1 and 2 for Examples 1 & 2
and Comparative Examples C-1 and C-2 show that the addition of
OPPERA.TM. PR 100A at 10 weight % enables one to increase the
attenuator pressure from 7 psig (about 48,263 Pa) to 18 psig
(124,106 Pa), thereby increasing the drawing of the filaments and
thereby decreasing the Actual Filament Diameter without any
filament breakage or "snapping" at a constant throughput. At the
higher attenuator pressure, we were able to obtain filament sizes
in the melt-spun (spun-bond) media of .about.4.6 microns at the
same rate as for Comparative Example C-2, even though the filament
spinning speed increases considerably, from 1464 to 2660 m/min,
between Comparative Examples C-2 and Example 2. The
stiffness/thickness ratio of the melt-spun (spun-bond) nonwoven web
also increases from 3.59 to 4.59 comparing Comparative Example C-1
and Example 1 at the same attenuator pressure of 2 psig (about
13,790 Pa).
[0214] While not wishing to be bound by any particular theory, it
appears that the addition of OPPERA.TM. PR 100A allows the
filaments to be stretched and oriented more, as is evident from the
filament spinning speed increase and decrease in filament size for
Example 2 relative to Comparative Example C-2. This high
orientation of the filament also leads to a considerable increase
in the ratio of stiffness/thickness, which increases from 2.55 g/m
to 8.36 g/m, as well as the tensile properties of the nonwoven web.
In fact, the maximum tensile load to break in the machine direction
(MD) doubles from 72.99N to 143.61N.
[0215] Furthermore, as can be seen from Tables 1 and 2, the
addition of OPPERA.TM. PR 100A at 10 weight % helps to increase the
throughput from 10 lbs/hr (about 4.55 kg/hr) to 25 lbs/hr (about
11.36 kg/hr), without a considerable change in the Actual Filament
Diameter. Therefore, the OPPERA.TM. additive can be used to
increase the throughput of the melt-spinning process without
significantly altering the desired Actual Filament Diameter.
[0216] It was also observed that at higher throughput rates, the
enhanced degree of molecular orientation in the filaments is even
more evident from the increase in filament spinning speed from 1464
to 3159 m/min. This considerable increase in orientation also leads
to an increase in the stiffness properties of the nonwoven web. As
the stiffness/thickness ratio increases from 2.55 g/m to 10.12 g/m,
which is a 4-fold increase in stiffness. The higher orientation of
filaments at higher rates also leads to considerable increase in
tensile properties as the maximum load (N) to break in MD increases
from 72.99 N to 120.1 N.
[0217] Additionally, as can be seen from Table 1, Comparative
Example C-1 and Examples 1 and 4 were all carried out at the same
throughput and same attenuation pressure which leads to a similar
filament spinning speed. However, the stiffness of the webs
increases with increasing OPPERA.TM. PR 100A weight percentage. The
ratio of stiffness to thickness increases from 3.59 g/m (0%
OPPERA.TM. PR 100A) to 4.59 g/m (10% OPPERA.TM. PR 100A) to 7.93
g/m (20% OPPERA.TM. PR 100A).
[0218] Furthermore, by increasing the OPPERA.TM. PR 100A
concentration to 20 weight %, we were able to increase the pressure
of the attenuator to 40 psig (about 275,790 Pa) compared to 7 psig
(about 48,263 Pa) for Comparative Example C-2. At that higher
attenuator pressure, we still did not observe any significant
filament breakage. Increasing the amount of OPPERA.TM. PR 100A thus
leads to smaller Actual Filament Diameter and increased throughput
ratek, because we can increase the attenuator pressure to draw the
filaments more.
[0219] In fact, at 20 weight % OPPERA.TM. PR 100A, we were able to
obtain filament diameters of 5.2 microns at a very high spinning
speed of 4159 m/min compared to Comparative Example C-2. The
stiffness/thickness ratio of the nonwoven web also increased from
2.55 to 11.30, and the maximum tensile load (N) to break in the
machine direction (MD) of the nonwoven web increased from 72.99 N
to 147.44 N.
[0220] Reference throughout this specification to "one embodiment,"
"certain embodiments," "one or more embodiments" or "an
embodiment," whether or not including the term "exemplary"
preceding the term "embodiment," means that a particular feature,
structure, material, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
certain exemplary embodiments of the present disclosure. Thus, the
appearances of the phrases such as "in one or more embodiments,"
"in certain embodiments," "in one embodiment" or "in an embodiment"
in various places throughout this specification are not necessarily
referring to the same embodiment of the certain exemplary
embodiments of the present disclosure. Furthermore, the particular
features, structures, materials, or characteristics may be combined
in any suitable manner in one or more embodiments.
[0221] While the specification has described in detail certain
exemplary embodiments, it will be appreciated that those skilled in
the art, upon attaining an understanding of the foregoing, may
readily conceive of alterations to, variations of, and equivalents
to these embodiments. Accordingly, it should be understood that
this disclosure is not to be unduly limited to the illustrative
embodiments set forth hereinabove. In addition, all numbers used
herein are assumed to be modified by the term "about."
[0222] Furthermore, all publications and patents referenced herein
are incorporated by reference in their entirety to the same extent
as if each individual publication or patent was specifically and
individually indicated to be incorporated by reference. Various
exemplary embodiments have been described. These and other
embodiments are within the scope of the following claims.
* * * * *